merge(3p/git): Merge git subtree at v2.29.2 r/1890

This also bumps the stable nixpkgs to 20.09 as of 2020-11-21, because
there is some breakage in the git build related to the netrc
credentials helper which someone has taken care of in nixpkgs.

The stable channel is not used for anything other than git, so this
should be fine.

Change-Id: I3575a19dab09e1e9556cf8231d717de9890484fb

13 files changed, 1031 insertions, 279 deletions

diff --git a/third_party/git/git-gui/lib/blame.tcl b/third_party/git/git-gui/lib/blame.tcl
index a1aeb8b96e2d..8441e109be32 100644
--- a/third_party/git/git-gui/lib/blame.tcl
+++ b/third_party/git/git-gui/lib/blame.tcl
@@ -24,6 +24,7 @@ field w_cviewer  ; # pane showing commit message
 field finder     ; # find mini-dialog frame
 field gotoline   ; # line goto mini-dialog frame
 field status     ; # status mega-widget instance
+field status_operation ; # operation displayed by status mega-widget
 field old_height ; # last known height of $w.file_pane
 
 
@@ -274,6 +275,7 @@ constructor new {i_commit i_path i_jump} {
 	pack $w_cviewer -expand 1 -fill both
 
 	set status [::status_bar::new $w.status]
+	set status_operation {}
 
 	menu $w.ctxm -tearoff 0
 	$w.ctxm add command \
@@ -326,6 +328,7 @@ constructor new {i_commit i_path i_jump} {
 		bind $i <Any-Motion>  [cb _show_tooltip $i @%x,%y]
 		bind $i <Any-Enter>   [cb _hide_tooltip]
 		bind $i <Any-Leave>   [cb _hide_tooltip]
+		bind $i <Deactivate>  [cb _hide_tooltip]
 		bind_button3 $i "
 			[cb _hide_tooltip]
 			set cursorX %x
@@ -602,16 +605,23 @@ method _exec_blame {cur_w cur_d options cur_s} {
 	} else {
 		lappend options $commit
 	}
+
+	# We may recurse in from another call to _exec_blame and already have
+	# a status operation.
+	if {$status_operation == {}} {
+		set status_operation [$status start \
+			$cur_s \
+			[mc "lines annotated"]]
+	} else {
+		$status_operation restart $cur_s
+	}
+
 	lappend options -- $path
 	set fd [eval git_read --nice blame $options]
 	fconfigure $fd -blocking 0 -translation lf -encoding utf-8
 	fileevent $fd readable [cb _read_blame $fd $cur_w $cur_d]
 	set current_fd $fd
 	set blame_lines 0
-
-	$status start \
-		$cur_s \
-		[mc "lines annotated"]
 }
 
 method _read_blame {fd cur_w cur_d} {
@@ -806,10 +816,11 @@ method _read_blame {fd cur_w cur_d} {
 				[mc "Loading original location annotations..."]
 		} else {
 			set current_fd {}
-			$status stop [mc "Annotation complete."]
+			$status_operation stop [mc "Annotation complete."]
+			set status_operation {}
 		}
 	} else {
-		$status update $blame_lines $total_lines
+		$status_operation update $blame_lines $total_lines
 	}
 } ifdeleted { catch {close $fd} }
 
@@ -1124,7 +1135,7 @@ method _blameparent {} {
 			set diffcmd [list diff-tree --unified=0 $cparent $cmit -- $new_path]
 		}
 		if {[catch {set fd [eval git_read $diffcmd]} err]} {
-			$status stop [mc "Unable to display parent"]
+			$status_operation stop [mc "Unable to display parent"]
 			error_popup [strcat [mc "Error loading diff:"] "\n\n$err"]
 			return
 		}
diff --git a/third_party/git/git-gui/lib/branch.tcl b/third_party/git/git-gui/lib/branch.tcl
index 777eeb79c135..8b0c4858890f 100644
--- a/third_party/git/git-gui/lib/branch.tcl
+++ b/third_party/git/git-gui/lib/branch.tcl
@@ -8,6 +8,7 @@ proc load_all_heads {} {
 	set rh_len [expr {[string length $rh] + 1}]
 	set all_heads [list]
 	set fd [git_read for-each-ref --format=%(refname) $rh]
+	fconfigure $fd -translation binary -encoding utf-8
 	while {[gets $fd line] > 0} {
 		if {!$some_heads_tracking || ![is_tracking_branch $line]} {
 			lappend all_heads [string range $line $rh_len end]
@@ -24,6 +25,7 @@ proc load_all_tags {} {
 		--sort=-taggerdate \
 		--format=%(refname) \
 		refs/tags]
+	fconfigure $fd -translation binary -encoding utf-8
 	while {[gets $fd line] > 0} {
 		if {![regsub ^refs/tags/ $line {} name]} continue
 		lappend all_tags $name
diff --git a/third_party/git/git-gui/lib/checkout_op.tcl b/third_party/git/git-gui/lib/checkout_op.tcl
index 9e7412c446f7..21ea768d8036 100644
--- a/third_party/git/git-gui/lib/checkout_op.tcl
+++ b/third_party/git/git-gui/lib/checkout_op.tcl
@@ -341,9 +341,9 @@ method _readtree {} {
 	global HEAD
 
 	set readtree_d {}
-	$::main_status start \
+	set status_bar_operation [$::main_status start \
 		[mc "Updating working directory to '%s'..." [_name $this]] \
-		[mc "files checked out"]
+		[mc "files checked out"]]
 
 	set fd [git_read --stderr read-tree \
 		-m \
@@ -354,26 +354,27 @@ method _readtree {} {
 		$new_hash \
 		]
 	fconfigure $fd -blocking 0 -translation binary
-	fileevent $fd readable [cb _readtree_wait $fd]
+	fileevent $fd readable [cb _readtree_wait $fd $status_bar_operation]
 }
 
-method _readtree_wait {fd} {
+method _readtree_wait {fd status_bar_operation} {
 	global current_branch
 
 	set buf [read $fd]
-	$::main_status update_meter $buf
+	$status_bar_operation update_meter $buf
 	append readtree_d $buf
 
 	fconfigure $fd -blocking 1
 	if {![eof $fd]} {
 		fconfigure $fd -blocking 0
+		$status_bar_operation stop
 		return
 	}
 
 	if {[catch {close $fd}]} {
 		set err $readtree_d
 		regsub {^fatal: } $err {} err
-		$::main_status stop [mc "Aborted checkout of '%s' (file level merging is required)." [_name $this]]
+		$status_bar_operation stop [mc "Aborted checkout of '%s' (file level merging is required)." [_name $this]]
 		warn_popup [strcat [mc "File level merge required."] "
 
 $err
@@ -384,12 +385,12 @@ $err
 		return
 	}
 
-	$::main_status stop
+	$status_bar_operation stop
 	_after_readtree $this
 }
 
 method _after_readtree {} {
-	global selected_commit_type commit_type HEAD MERGE_HEAD PARENT
+	global commit_type HEAD MERGE_HEAD PARENT
 	global current_branch is_detached
 	global ui_comm
 
@@ -490,12 +491,12 @@ method _update_repo_state {} {
 	#    amend mode our file lists are accurate and we can avoid
 	#    the rescan.
 	#
-	global selected_commit_type commit_type HEAD MERGE_HEAD PARENT
+	global commit_type_is_amend commit_type HEAD MERGE_HEAD PARENT
 	global ui_comm
 
 	unlock_index
 	set name [_name $this]
-	set selected_commit_type new
+	set commit_type_is_amend 0
 	if {[string match amend* $commit_type]} {
 		$ui_comm delete 0.0 end
 		$ui_comm edit reset
diff --git a/third_party/git/git-gui/lib/choose_repository.tcl b/third_party/git/git-gui/lib/choose_repository.tcl
index 80f5a59bbbfc..af1fee7c751d 100644
--- a/third_party/git/git-gui/lib/choose_repository.tcl
+++ b/third_party/git/git-gui/lib/choose_repository.tcl
@@ -9,6 +9,18 @@ field w_body      ; # Widget holding the center content
 field w_next      ; # Next button
 field w_quit      ; # Quit button
 field o_cons      ; # Console object (if active)
+
+# Status mega-widget instance during _do_clone2 (used by _copy_files and
+# _link_files). Widget is destroyed before _do_clone2 calls
+# _do_clone_checkout
+field o_status
+
+# Operation displayed by status mega-widget during _do_clone_checkout =>
+# _readtree_wait => _postcheckout_wait => _do_clone_submodules =>
+# _do_validate_submodule_cloning. The status mega-widget is a different
+# instance than that stored in $o_status in earlier operations.
+field o_status_op
+
 field w_types     ; # List of type buttons in clone
 field w_recentlist ; # Listbox containing recent repositories
 field w_localpath  ; # Entry widget bound to local_path
@@ -345,31 +357,10 @@ proc _is_git {path {outdir_var ""}} {
 	if {$outdir_var ne ""} {
 		upvar 1 $outdir_var outdir
 	}
-	if {[file isfile $path]} {
-		set fp [open $path r]
-		gets $fp line
-		close $fp
-		if {[regexp "^gitdir: (.+)$" $line line link_target]} {
-			set path [file join [file dirname $path] $link_target]
-			set path [file normalize $path]
-		}
-	}
-
-	if {[file exists [file join $path HEAD]]
-	 && [file exists [file join $path objects]]
-	 && [file exists [file join $path config]]} {
-		set outdir $path
-		return 1
-	}
-	if {[is_Cygwin]} {
-		if {[file exists [file join $path HEAD]]
-		 && [file exists [file join $path objects.lnk]]
-		 && [file exists [file join $path config.lnk]]} {
-			set outdir $path
-			return 1
-		}
+	if {[catch {set outdir [git rev-parse --resolve-git-dir $path]}]} {
+		return 0
 	}
-	return 0
+	return 1
 }
 
 proc _objdir {path} {
@@ -659,12 +650,12 @@ method _do_clone2 {} {
 
 	switch -exact -- $clone_type {
 	hardlink {
-		set o_cons [status_bar::two_line $w_body]
+		set o_status [status_bar::two_line $w_body]
 		pack $w_body -fill x -padx 10 -pady 10
 
-		$o_cons start \
+		set status_op [$o_status start \
 			[mc "Counting objects"] \
-			[mc "buckets"]
+			[mc "buckets"]]
 		update
 
 		if {[file exists [file join $objdir info alternates]]} {
@@ -689,6 +680,7 @@ method _do_clone2 {} {
 			} err]} {
 				catch {cd $pwd}
 				_clone_failed $this [mc "Unable to copy objects/info/alternates: %s" $err]
+				$status_op stop
 				return
 			}
 		}
@@ -700,7 +692,7 @@ method _do_clone2 {} {
 			-directory [file join $objdir] ??]
 		set bcnt [expr {[llength $buckets] + 2}]
 		set bcur 1
-		$o_cons update $bcur $bcnt
+		$status_op update $bcur $bcnt
 		update
 
 		file mkdir [file join .git objects pack]
@@ -708,7 +700,7 @@ method _do_clone2 {} {
 			-directory [file join $objdir pack] *] {
 			lappend tolink [file join pack $i]
 		}
-		$o_cons update [incr bcur] $bcnt
+		$status_op update [incr bcur] $bcnt
 		update
 
 		foreach i $buckets {
@@ -717,10 +709,10 @@ method _do_clone2 {} {
 				-directory [file join $objdir $i] *] {
 				lappend tolink [file join $i $j]
 			}
-			$o_cons update [incr bcur] $bcnt
+			$status_op update [incr bcur] $bcnt
 			update
 		}
-		$o_cons stop
+		$status_op stop
 
 		if {$tolink eq {}} {
 			info_popup [strcat \
@@ -747,6 +739,8 @@ method _do_clone2 {} {
 		if {!$i} return
 
 		destroy $w_body
+
+		set o_status {}
 	}
 	full {
 		set o_cons [console::embed \
@@ -781,9 +775,9 @@ method _do_clone2 {} {
 }
 
 method _copy_files {objdir tocopy} {
-	$o_cons start \
+	set status_op [$o_status start \
 		[mc "Copying objects"] \
-		[mc "KiB"]
+		[mc "KiB"]]
 	set tot 0
 	set cmp 0
 	foreach p $tocopy {
@@ -798,7 +792,7 @@ method _copy_files {objdir tocopy} {
 
 				while {![eof $f_in]} {
 					incr cmp [fcopy $f_in $f_cp -size 16384]
-					$o_cons update \
+					$status_op update \
 						[expr {$cmp / 1024}] \
 						[expr {$tot / 1024}]
 					update
@@ -808,17 +802,19 @@ method _copy_files {objdir tocopy} {
 				close $f_cp
 			} err]} {
 			_clone_failed $this [mc "Unable to copy object: %s" $err]
+			$status_op stop
 			return 0
 		}
 	}
+	$status_op stop
 	return 1
 }
 
 method _link_files {objdir tolink} {
 	set total [llength $tolink]
-	$o_cons start \
+	set status_op [$o_status start \
 		[mc "Linking objects"] \
-		[mc "objects"]
+		[mc "objects"]]
 	for {set i 0} {$i < $total} {} {
 		set p [lindex $tolink $i]
 		if {[catch {
@@ -827,15 +823,17 @@ method _link_files {objdir tolink} {
 					[file join $objdir $p]
 			} err]} {
 			_clone_failed $this [mc "Unable to hardlink object: %s" $err]
+			$status_op stop
 			return 0
 		}
 
 		incr i
 		if {$i % 5 == 0} {
-			$o_cons update $i $total
+			$status_op update $i $total
 			update
 		}
 	}
+	$status_op stop
 	return 1
 }
 
@@ -958,11 +956,26 @@ method _do_clone_checkout {HEAD} {
 		return
 	}
 
-	set o_cons [status_bar::two_line $w_body]
+	set status [status_bar::two_line $w_body]
 	pack $w_body -fill x -padx 10 -pady 10
-	$o_cons start \
+
+	# We start the status operation here.
+	#
+	# This function calls _readtree_wait as a callback.
+	#
+	# _readtree_wait in turn either calls _do_clone_submodules directly,
+	# or calls _postcheckout_wait as a callback which then calls
+	# _do_clone_submodules.
+	#
+	# _do_clone_submodules calls _do_validate_submodule_cloning.
+	#
+	# _do_validate_submodule_cloning stops the status operation.
+	#
+	# There are no other calls into this chain from other code.
+
+	set o_status_op [$status start \
 		[mc "Creating working directory"] \
-		[mc "files"]
+		[mc "files"]]
 
 	set readtree_err {}
 	set fd [git_read --stderr read-tree \
@@ -976,33 +989,9 @@ method _do_clone_checkout {HEAD} {
 	fileevent $fd readable [cb _readtree_wait $fd]
 }
 
-method _do_validate_submodule_cloning {ok} {
-	if {$ok} {
-		$o_cons done $ok
-		set done 1
-	} else {
-		_clone_failed $this [mc "Cannot clone submodules."]
-	}
-}
-
-method _do_clone_submodules {} {
-	if {$recursive eq {true}} {
-		destroy $w_body
-		set o_cons [console::embed \
-			$w_body \
-			[mc "Cloning submodules"]]
-		pack $w_body -fill both -expand 1 -padx 10
-		$o_cons exec \
-			[list git submodule update --init --recursive] \
-			[cb _do_validate_submodule_cloning]
-	} else {
-		set done 1
-	}
-}
-
 method _readtree_wait {fd} {
 	set buf [read $fd]
-	$o_cons update_meter $buf
+	$o_status_op update_meter $buf
 	append readtree_err $buf
 
 	fconfigure $fd -blocking 1
@@ -1050,6 +1039,34 @@ method _postcheckout_wait {fd_ph} {
 	fconfigure $fd_ph -blocking 0
 }
 
+method _do_clone_submodules {} {
+	if {$recursive eq {true}} {
+		$o_status_op stop
+		set o_status_op {}
+
+		destroy $w_body
+
+		set o_cons [console::embed \
+			$w_body \
+			[mc "Cloning submodules"]]
+		pack $w_body -fill both -expand 1 -padx 10
+		$o_cons exec \
+			[list git submodule update --init --recursive] \
+			[cb _do_validate_submodule_cloning]
+	} else {
+		set done 1
+	}
+}
+
+method _do_validate_submodule_cloning {ok} {
+	if {$ok} {
+		$o_cons done $ok
+		set done 1
+	} else {
+		_clone_failed $this [mc "Cannot clone submodules."]
+	}
+}
+
 ######################################################################
 ##
 ## Open Existing Repository
diff --git a/third_party/git/git-gui/lib/chord.tcl b/third_party/git/git-gui/lib/chord.tcl
new file mode 100644
index 000000000000..e21e7d3d0b79
--- /dev/null
+++ b/third_party/git/git-gui/lib/chord.tcl
@@ -0,0 +1,158 @@
+# Simple Chord for Tcl
+#
+# A "chord" is a method with more than one entrypoint and only one body, such
+# that the body runs only once all the entrypoints have been called by
+# different asynchronous tasks. In this implementation, the chord is defined
+# dynamically for each invocation. A SimpleChord object is created, supplying
+# body script to be run when the chord is completed, and then one or more notes
+# are added to the chord. Each note can be called like a proc, and returns
+# immediately if the chord isn't yet complete. When the last remaining note is
+# called, the body runs before the note returns.
+#
+# The SimpleChord class has a constructor that takes the body script, and a
+# method add_note that returns a note object. Since the body script does not
+# run in the context of the procedure that defined it, a mechanism is provided
+# for injecting variables into the chord for use by the body script. The
+# activation of a note is idempotent; multiple calls have the same effect as
+# a simple call.
+#
+# If you are invoking asynchronous operations with chord notes as completion
+# callbacks, and there is a possibility that earlier operations could complete
+# before later ones are started, it is a good practice to create a "common"
+# note on the chord that prevents it from being complete until you're certain
+# you've added all the notes you need.
+#
+# Example:
+#
+#   # Turn off the UI while running a couple of async operations.
+#   lock_ui
+#
+#   set chord [SimpleChord::new {
+#     unlock_ui
+#     # Note: $notice here is not referenced in the calling scope
+#     if {$notice} { info_popup $notice }
+#   }
+#
+#   # Configure a note to keep the chord from completing until
+#   # all operations have been initiated.
+#   set common_note [$chord add_note]
+#
+#   # Activate notes in 'after' callbacks to other operations
+#   set newnote [$chord add_note]
+#   async_operation $args [list $newnote activate]
+#
+#   # Communicate with the chord body
+#   if {$condition} {
+#     # This sets $notice in the same context that the chord body runs in.
+#     $chord eval { set notice "Something interesting" }
+#   }
+#
+#   # Activate the common note, making the chord eligible to complete
+#   $common_note activate
+#
+# At this point, the chord will complete at some unknown point in the future.
+# The common note might have been the first note activated, or the async
+# operations might have completed synchronously and the common note is the
+# last one, completing the chord before this code finishes, or anything in
+# between. The purpose of the chord is to not have to worry about the order.
+
+# SimpleChord class:
+#   Represents a procedure that conceptually has multiple entrypoints that must
+#   all be called before the procedure executes. Each entrypoint is called a
+#   "note". The chord is only "completed" when all the notes are "activated".
+class SimpleChord {
+	field notes
+	field body
+	field is_completed
+	field eval_ns
+
+	# Constructor:
+	#   set chord [SimpleChord::new {body}]
+	#     Creates a new chord object with the specified body script. The
+	#     body script is evaluated at most once, when a note is activated
+	#     and the chord has no other non-activated notes.
+	constructor new {i_body} {
+		set notes [list]
+		set body $i_body
+		set is_completed 0
+		set eval_ns "[namespace qualifiers $this]::eval"
+		return $this
+	}
+
+	# Method:
+	#   $chord eval {script}
+	#     Runs the specified script in the same context (namespace) in which
+	#     the chord body will be evaluated. This can be used to set variable
+	#     values for the chord body to use.
+	method eval {script} {
+		namespace eval $eval_ns $script
+	}
+
+	# Method:
+	#   set note [$chord add_note]
+	#     Adds a new note to the chord, an instance of ChordNote. Raises an
+	#     error if the chord is already completed, otherwise the chord is
+	#     updated so that the new note must also be activated before the
+	#     body is evaluated.
+	method add_note {} {
+		if {$is_completed} { error "Cannot add a note to a completed chord" }
+
+		set note [ChordNote::new $this]
+
+		lappend notes $note
+
+		return $note
+	}
+
+	# This method is for internal use only and is intentionally undocumented.
+	method notify_note_activation {} {
+		if {!$is_completed} {
+			foreach note $notes {
+				if {![$note is_activated]} { return }
+			}
+
+			set is_completed 1
+
+			namespace eval $eval_ns $body
+			delete_this
+		}
+	}
+}
+
+# ChordNote class:
+#   Represents a note within a chord, providing a way to activate it. When the
+#   final note of the chord is activated (this can be any note in the chord,
+#   with all other notes already previously activated in any order), the chord's
+#   body is evaluated.
+class ChordNote {
+	field chord
+	field is_activated
+
+	# Constructor:
+	#   Instances of ChordNote are created internally by calling add_note on
+	#   SimpleChord objects.
+	constructor new {c} {
+		set chord $c
+		set is_activated 0
+		return $this
+	}
+
+	# Method:
+	#   [$note is_activated]
+	#     Returns true if this note has already been activated.
+	method is_activated {} {
+		return $is_activated
+	}
+
+	# Method:
+	#   $note activate
+	#     Activates the note, if it has not already been activated, and
+	#     completes the chord if there are no other notes awaiting
+	#     activation. Subsequent calls will have no further effect.
+	method activate {} {
+		if {!$is_activated} {
+			set is_activated 1
+			$chord notify_note_activation
+		}
+	}
+}
diff --git a/third_party/git/git-gui/lib/commit.tcl b/third_party/git/git-gui/lib/commit.tcl
index 75ea965dacd7..b516aa299069 100644
--- a/third_party/git/git-gui/lib/commit.tcl
+++ b/third_party/git/git-gui/lib/commit.tcl
@@ -333,7 +333,7 @@ proc commit_writetree {curHEAD msg_p} {
 proc commit_committree {fd_wt curHEAD msg_p} {
 	global HEAD PARENT MERGE_HEAD commit_type commit_author
 	global current_branch
-	global ui_comm selected_commit_type
+	global ui_comm commit_type_is_amend
 	global file_states selected_paths rescan_active
 	global repo_config
 	global env
@@ -467,8 +467,8 @@ A rescan will be automatically started now.
 
 	# -- Update in memory status
 	#
-	set selected_commit_type new
 	set commit_type normal
+	set commit_type_is_amend 0
 	set HEAD $cmt_id
 	set PARENT $cmt_id
 	set MERGE_HEAD [list]
diff --git a/third_party/git/git-gui/lib/console.tcl b/third_party/git/git-gui/lib/console.tcl
index 1f3248ffd113..bb6b9c889e20 100644
--- a/third_party/git/git-gui/lib/console.tcl
+++ b/third_party/git/git-gui/lib/console.tcl
@@ -203,6 +203,8 @@ method done {ok} {
 			focus $w.ok
 		}
 	}
+
+	bind $w <Key-Escape> "destroy $w;break"
 }
 
 method _sb_set {sb orient first last} {
diff --git a/third_party/git/git-gui/lib/diff.tcl b/third_party/git/git-gui/lib/diff.tcl
index 68c4a6c7366f..871ad488c2a1 100644
--- a/third_party/git/git-gui/lib/diff.tcl
+++ b/third_party/git/git-gui/lib/diff.tcl
@@ -55,7 +55,7 @@ proc reshow_diff {{after {}}} {
 
 proc force_diff_encoding {enc} {
 	global current_diff_path
-	
+
 	if {$current_diff_path ne {}} {
 		force_path_encoding $current_diff_path $enc
 		reshow_diff
@@ -270,19 +270,6 @@ proc show_other_diff {path w m cont_info} {
 	}
 }
 
-proc get_conflict_marker_size {path} {
-	set size 7
-	catch {
-		set fd_rc [eval [list git_read check-attr "conflict-marker-size" -- $path]]
-		set ret [gets $fd_rc line]
-		close $fd_rc
-		if {$ret > 0} {
-			regexp {.*: conflict-marker-size: (\d+)$} $line line size
-		}
-	}
-	return $size
-}
-
 proc start_show_diff {cont_info {add_opts {}}} {
 	global file_states file_lists
 	global is_3way_diff is_submodule_diff diff_active repo_config
@@ -298,7 +285,7 @@ proc start_show_diff {cont_info {add_opts {}}} {
 	set is_submodule_diff 0
 	set diff_active 1
 	set current_diff_header {}
-	set conflict_size [get_conflict_marker_size $path]
+	set conflict_size [gitattr $path conflict-marker-size 7]
 
 	set cmd [list]
 	if {$w eq $ui_index} {
@@ -360,6 +347,10 @@ proc start_show_diff {cont_info {add_opts {}}} {
 	}
 
 	set ::current_diff_inheader 1
+	# Detect pre-image lines of the diff3 conflict-style. They are just
+	# '++' lines which is not bijective. Thus, we need to maintain a state
+	# across lines.
+	set ::conflict_in_pre_image 0
 	fconfigure $fd \
 		-blocking 0 \
 		-encoding [get_path_encoding $path] \
@@ -462,11 +453,23 @@ proc read_diff {fd conflict_size cont_info} {
 			{--} {set tags d_--}
 			{++} {
 				set regexp [string map [list %conflict_size $conflict_size]\
-								{^\+\+([<>=]){%conflict_size}(?: |$)}]
+								{^\+\+([<>=|]){%conflict_size}(?: |$)}]
 				if {[regexp $regexp $line _g op]} {
 					set is_conflict_diff 1
 					set line [string replace $line 0 1 {  }]
 					set tags d$op
+
+					# The ||| conflict-marker marks the start of the pre-image.
+					# All those lines are also prefixed with '++'. Thus we need
+					# to maintain this state.
+					set ::conflict_in_pre_image [expr {$op eq {|}}]
+				} elseif {$::conflict_in_pre_image} {
+					# This is a pre-image line. It is the one which both sides
+					# are based on. As it has also the '++' line start, it is
+					# normally shown as 'added'. Invert this to '--' to make
+					# it a 'removed' line.
+					set line [string replace $line 0 1 {--}]
+					set tags d_--
 				} else {
 					set tags d_++
 				}
@@ -567,24 +570,31 @@ proc read_diff {fd conflict_size cont_info} {
 	}
 }
 
-proc apply_hunk {x y} {
+proc apply_or_revert_hunk {x y revert} {
 	global current_diff_path current_diff_header current_diff_side
-	global ui_diff ui_index file_states
+	global ui_diff ui_index file_states last_revert last_revert_enc
 
 	if {$current_diff_path eq {} || $current_diff_header eq {}} return
 	if {![lock_index apply_hunk]} return
 
-	set apply_cmd {apply --cached --whitespace=nowarn}
+	set apply_cmd {apply --whitespace=nowarn}
 	set mi [lindex $file_states($current_diff_path) 0]
 	if {$current_diff_side eq $ui_index} {
 		set failed_msg [mc "Failed to unstage selected hunk."]
-		lappend apply_cmd --reverse
+		lappend apply_cmd --reverse --cached
 		if {[string index $mi 0] ne {M}} {
 			unlock_index
 			return
 		}
 	} else {
-		set failed_msg [mc "Failed to stage selected hunk."]
+		if {$revert} {
+			set failed_msg [mc "Failed to revert selected hunk."]
+			lappend apply_cmd --reverse
+		} else {
+			set failed_msg [mc "Failed to stage selected hunk."]
+			lappend apply_cmd --cached
+		}
+
 		if {[string index $mi 1] ne {M}} {
 			unlock_index
 			return
@@ -603,29 +613,40 @@ proc apply_hunk {x y} {
 		set e_lno end
 	}
 
+	set wholepatch "$current_diff_header[$ui_diff get $s_lno $e_lno]"
+
 	if {[catch {
 		set enc [get_path_encoding $current_diff_path]
 		set p [eval git_write $apply_cmd]
 		fconfigure $p -translation binary -encoding $enc
-		puts -nonewline $p $current_diff_header
-		puts -nonewline $p [$ui_diff get $s_lno $e_lno]
+		puts -nonewline $p $wholepatch
 		close $p} err]} {
 		error_popup "$failed_msg\n\n$err"
 		unlock_index
 		return
 	}
 
+	if {$revert} {
+		# Save a copy of this patch for undoing reverts.
+		set last_revert $wholepatch
+		set last_revert_enc $enc
+	}
+
 	$ui_diff conf -state normal
 	$ui_diff delete $s_lno $e_lno
 	$ui_diff conf -state disabled
 
+	# Check if the hunk was the last one in the file.
 	if {[$ui_diff get 1.0 end] eq "\n"} {
 		set o _
 	} else {
 		set o ?
 	}
 
-	if {$current_diff_side eq $ui_index} {
+	# Update the status flags.
+	if {$revert} {
+		set mi [string index $mi 0]$o
+	} elseif {$current_diff_side eq $ui_index} {
 		set mi ${o}M
 	} elseif {[string index $mi 0] eq {_}} {
 		set mi M$o
@@ -640,9 +661,9 @@ proc apply_hunk {x y} {
 	}
 }
 
-proc apply_range_or_line {x y} {
+proc apply_or_revert_range_or_line {x y revert} {
 	global current_diff_path current_diff_header current_diff_side
-	global ui_diff ui_index file_states
+	global ui_diff ui_index file_states last_revert
 
 	set selected [$ui_diff tag nextrange sel 0.0]
 
@@ -660,19 +681,27 @@ proc apply_range_or_line {x y} {
 	if {$current_diff_path eq {} || $current_diff_header eq {}} return
 	if {![lock_index apply_hunk]} return
 
-	set apply_cmd {apply --cached --whitespace=nowarn}
+	set apply_cmd {apply --whitespace=nowarn}
 	set mi [lindex $file_states($current_diff_path) 0]
 	if {$current_diff_side eq $ui_index} {
 		set failed_msg [mc "Failed to unstage selected line."]
 		set to_context {+}
-		lappend apply_cmd --reverse
+		lappend apply_cmd --reverse --cached
 		if {[string index $mi 0] ne {M}} {
 			unlock_index
 			return
 		}
 	} else {
-		set failed_msg [mc "Failed to stage selected line."]
-		set to_context {-}
+		if {$revert} {
+			set failed_msg [mc "Failed to revert selected line."]
+			set to_context {+}
+			lappend apply_cmd --reverse
+		} else {
+			set failed_msg [mc "Failed to stage selected line."]
+			set to_context {-}
+			lappend apply_cmd --cached
+		}
+
 		if {[string index $mi 1] ne {M}} {
 			unlock_index
 			return
@@ -830,7 +859,47 @@ proc apply_range_or_line {x y} {
 		puts -nonewline $p $wholepatch
 		close $p} err]} {
 		error_popup "$failed_msg\n\n$err"
+		unlock_index
+		return
+	}
+
+	if {$revert} {
+		# Save a copy of this patch for undoing reverts.
+		set last_revert $current_diff_header$wholepatch
+		set last_revert_enc $enc
+	}
+
+	unlock_index
+}
+
+# Undo the last line/hunk reverted. When hunks and lines are reverted, a copy
+# of the diff applied is saved. Re-apply that diff to undo the revert.
+#
+# Right now, we only use a single variable to hold the copy, and not a
+# stack/deque for simplicity, so multiple undos are not possible. Maybe this
+# can be added if the need for something like this is felt in the future.
+proc undo_last_revert {} {
+	global last_revert current_diff_path current_diff_header
+	global last_revert_enc
+
+	if {$last_revert eq {}} return
+	if {![lock_index apply_hunk]} return
+
+	set apply_cmd {apply --whitespace=nowarn}
+	set failed_msg [mc "Failed to undo last revert."]
+
+	if {[catch {
+		set enc $last_revert_enc
+		set p [eval git_write $apply_cmd]
+		fconfigure $p -translation binary -encoding $enc
+		puts -nonewline $p $last_revert
+		close $p} err]} {
+		error_popup "$failed_msg\n\n$err"
+		unlock_index
+		return
 	}
 
+	set last_revert {}
+
 	unlock_index
 }
diff --git a/third_party/git/git-gui/lib/index.tcl b/third_party/git/git-gui/lib/index.tcl
index b588db11d9fc..d2ec24bd80e1 100644
--- a/third_party/git/git-gui/lib/index.tcl
+++ b/third_party/git/git-gui/lib/index.tcl
@@ -7,67 +7,74 @@ proc _delete_indexlock {} {
 	}
 }
 
-proc _close_updateindex {fd after} {
-	global use_ttk NS
-	fconfigure $fd -blocking 1
-	if {[catch {close $fd} err]} {
-		set w .indexfried
-		Dialog $w
-		wm withdraw $w
-		wm title $w [strcat "[appname] ([reponame]): " [mc "Index Error"]]
-		wm geometry $w "+[winfo rootx .]+[winfo rooty .]"
-		set s [mc "Updating the Git index failed.  A rescan will be automatically started to resynchronize git-gui."]
-		text $w.msg -yscrollcommand [list $w.vs set] \
-			-width [string length $s] -relief flat \
-			-borderwidth 0 -highlightthickness 0 \
-			-background [get_bg_color $w]
-		$w.msg tag configure bold -font font_uibold -justify center
-		${NS}::scrollbar $w.vs -command [list $w.msg yview]
-		$w.msg insert end $s bold \n\n$err {}
-		$w.msg configure -state disabled
-
-		${NS}::button $w.continue \
-			-text [mc "Continue"] \
-			-command [list destroy $w]
-		${NS}::button $w.unlock \
-			-text [mc "Unlock Index"] \
-			-command "destroy $w; _delete_indexlock"
-		grid $w.msg - $w.vs -sticky news
-		grid $w.unlock $w.continue - -sticky se -padx 2 -pady 2
-		grid columnconfigure $w 0 -weight 1
-		grid rowconfigure $w 0 -weight 1
-
-		wm protocol $w WM_DELETE_WINDOW update
-		bind $w.continue <Visibility> "
-			grab $w
-			focus %W
-		"
-		wm deiconify $w
-		tkwait window $w
-
-		$::main_status stop
+proc close_and_unlock_index {fd after} {
+	if {![catch {_close_updateindex $fd} err]} {
 		unlock_index
-		rescan $after 0
-		return
+		uplevel #0 $after
+	} else {
+		rescan_on_error $err $after
 	}
+}
 
-	$::main_status stop
+proc _close_updateindex {fd} {
+	fconfigure $fd -blocking 1
+	close $fd
+}
+
+proc rescan_on_error {err {after {}}} {
+	global use_ttk NS
+
+	set w .indexfried
+	Dialog $w
+	wm withdraw $w
+	wm title $w [strcat "[appname] ([reponame]): " [mc "Index Error"]]
+	wm geometry $w "+[winfo rootx .]+[winfo rooty .]"
+	set s [mc "Updating the Git index failed.  A rescan will be automatically started to resynchronize git-gui."]
+	text $w.msg -yscrollcommand [list $w.vs set] \
+		-width [string length $s] -relief flat \
+		-borderwidth 0 -highlightthickness 0 \
+		-background [get_bg_color $w]
+	$w.msg tag configure bold -font font_uibold -justify center
+	${NS}::scrollbar $w.vs -command [list $w.msg yview]
+	$w.msg insert end $s bold \n\n$err {}
+	$w.msg configure -state disabled
+
+	${NS}::button $w.continue \
+		-text [mc "Continue"] \
+		-command [list destroy $w]
+	${NS}::button $w.unlock \
+		-text [mc "Unlock Index"] \
+		-command "destroy $w; _delete_indexlock"
+	grid $w.msg - $w.vs -sticky news
+	grid $w.unlock $w.continue - -sticky se -padx 2 -pady 2
+	grid columnconfigure $w 0 -weight 1
+	grid rowconfigure $w 0 -weight 1
+
+	wm protocol $w WM_DELETE_WINDOW update
+	bind $w.continue <Visibility> "
+		grab $w
+		focus %W
+	"
+	wm deiconify $w
+	tkwait window $w
+
+	$::main_status stop_all
 	unlock_index
-	uplevel #0 $after
+	rescan [concat $after {ui_ready;}] 0
 }
 
-proc update_indexinfo {msg pathList after} {
+proc update_indexinfo {msg path_list after} {
 	global update_index_cp
 
 	if {![lock_index update]} return
 
 	set update_index_cp 0
-	set pathList [lsort $pathList]
-	set totalCnt [llength $pathList]
-	set batch [expr {int($totalCnt * .01) + 1}]
+	set path_list [lsort $path_list]
+	set total_cnt [llength $path_list]
+	set batch [expr {int($total_cnt * .01) + 1}]
 	if {$batch > 25} {set batch 25}
 
-	$::main_status start $msg [mc "files"]
+	set status_bar_operation [$::main_status start $msg [mc "files"]]
 	set fd [git_write update-index -z --index-info]
 	fconfigure $fd \
 		-blocking 0 \
@@ -78,26 +85,29 @@ proc update_indexinfo {msg pathList after} {
 	fileevent $fd writable [list \
 		write_update_indexinfo \
 		$fd \
-		$pathList \
-		$totalCnt \
+		$path_list \
+		$total_cnt \
 		$batch \
+		$status_bar_operation \
 		$after \
 		]
 }
 
-proc write_update_indexinfo {fd pathList totalCnt batch after} {
+proc write_update_indexinfo {fd path_list total_cnt batch status_bar_operation \
+	after} {
 	global update_index_cp
 	global file_states current_diff_path
 
-	if {$update_index_cp >= $totalCnt} {
-		_close_updateindex $fd $after
+	if {$update_index_cp >= $total_cnt} {
+		$status_bar_operation stop
+		close_and_unlock_index $fd $after
 		return
 	}
 
 	for {set i $batch} \
-		{$update_index_cp < $totalCnt && $i > 0} \
+		{$update_index_cp < $total_cnt && $i > 0} \
 		{incr i -1} {
-		set path [lindex $pathList $update_index_cp]
+		set path [lindex $path_list $update_index_cp]
 		incr update_index_cp
 
 		set s $file_states($path)
@@ -119,21 +129,21 @@ proc write_update_indexinfo {fd pathList totalCnt batch after} {
 		display_file $path $new
 	}
 
-	$::main_status update $update_index_cp $totalCnt
+	$status_bar_operation update $update_index_cp $total_cnt
 }
 
-proc update_index {msg pathList after} {
+proc update_index {msg path_list after} {
 	global update_index_cp
 
 	if {![lock_index update]} return
 
 	set update_index_cp 0
-	set pathList [lsort $pathList]
-	set totalCnt [llength $pathList]
-	set batch [expr {int($totalCnt * .01) + 1}]
+	set path_list [lsort $path_list]
+	set total_cnt [llength $path_list]
+	set batch [expr {int($total_cnt * .01) + 1}]
 	if {$batch > 25} {set batch 25}
 
-	$::main_status start $msg [mc "files"]
+	set status_bar_operation [$::main_status start $msg [mc "files"]]
 	set fd [git_write update-index --add --remove -z --stdin]
 	fconfigure $fd \
 		-blocking 0 \
@@ -144,26 +154,29 @@ proc update_index {msg pathList after} {
 	fileevent $fd writable [list \
 		write_update_index \
 		$fd \
-		$pathList \
-		$totalCnt \
+		$path_list \
+		$total_cnt \
 		$batch \
+		$status_bar_operation \
 		$after \
 		]
 }
 
-proc write_update_index {fd pathList totalCnt batch after} {
+proc write_update_index {fd path_list total_cnt batch status_bar_operation \
+	after} {
 	global update_index_cp
 	global file_states current_diff_path
 
-	if {$update_index_cp >= $totalCnt} {
-		_close_updateindex $fd $after
+	if {$update_index_cp >= $total_cnt} {
+		$status_bar_operation stop
+		close_and_unlock_index $fd $after
 		return
 	}
 
 	for {set i $batch} \
-		{$update_index_cp < $totalCnt && $i > 0} \
+		{$update_index_cp < $total_cnt && $i > 0} \
 		{incr i -1} {
-		set path [lindex $pathList $update_index_cp]
+		set path [lindex $path_list $update_index_cp]
 		incr update_index_cp
 
 		switch -glob -- [lindex $file_states($path) 0] {
@@ -190,21 +203,21 @@ proc write_update_index {fd pathList totalCnt batch after} {
 		display_file $path $new
 	}
 
-	$::main_status update $update_index_cp $totalCnt
+	$status_bar_operation update $update_index_cp $total_cnt
 }
 
-proc checkout_index {msg pathList after} {
+proc checkout_index {msg path_list after capture_error} {
 	global update_index_cp
 
 	if {![lock_index update]} return
 
 	set update_index_cp 0
-	set pathList [lsort $pathList]
-	set totalCnt [llength $pathList]
-	set batch [expr {int($totalCnt * .01) + 1}]
+	set path_list [lsort $path_list]
+	set total_cnt [llength $path_list]
+	set batch [expr {int($total_cnt * .01) + 1}]
 	if {$batch > 25} {set batch 25}
 
-	$::main_status start $msg [mc "files"]
+	set status_bar_operation [$::main_status start $msg [mc "files"]]
 	set fd [git_write checkout-index \
 		--index \
 		--quiet \
@@ -221,26 +234,45 @@ proc checkout_index {msg pathList after} {
 	fileevent $fd writable [list \
 		write_checkout_index \
 		$fd \
-		$pathList \
-		$totalCnt \
+		$path_list \
+		$total_cnt \
 		$batch \
+		$status_bar_operation \
 		$after \
+		$capture_error \
 		]
 }
 
-proc write_checkout_index {fd pathList totalCnt batch after} {
+proc write_checkout_index {fd path_list total_cnt batch status_bar_operation \
+	after capture_error} {
 	global update_index_cp
 	global file_states current_diff_path
 
-	if {$update_index_cp >= $totalCnt} {
-		_close_updateindex $fd $after
+	if {$update_index_cp >= $total_cnt} {
+		$status_bar_operation stop
+
+		# We do not unlock the index directly here because this
+		# operation expects to potentially run in parallel with file
+		# deletions scheduled by revert_helper. We're done with the
+		# update index, so we close it, but actually unlocking the index
+		# and dealing with potential errors is deferred to the chord
+		# body that runs when all async operations are completed.
+		#
+		# (See after_chord in revert_helper.)
+
+		if {[catch {_close_updateindex $fd} err]} {
+			uplevel #0 $capture_error [list $err]
+		}
+
+		uplevel #0 $after
+
 		return
 	}
 
 	for {set i $batch} \
-		{$update_index_cp < $totalCnt && $i > 0} \
+		{$update_index_cp < $total_cnt && $i > 0} \
 		{incr i -1} {
-		set path [lindex $pathList $update_index_cp]
+		set path [lindex $path_list $update_index_cp]
 		incr update_index_cp
 		switch -glob -- [lindex $file_states($path) 0] {
 		U? {continue}
@@ -253,7 +285,7 @@ proc write_checkout_index {fd pathList totalCnt batch after} {
 		}
 	}
 
-	$::main_status update $update_index_cp $totalCnt
+	$status_bar_operation update $update_index_cp $total_cnt
 }
 
 proc unstage_helper {txt paths} {
@@ -261,7 +293,7 @@ proc unstage_helper {txt paths} {
 
 	if {![lock_index begin-update]} return
 
-	set pathList [list]
+	set path_list [list]
 	set after {}
 	foreach path $paths {
 		switch -glob -- [lindex $file_states($path) 0] {
@@ -269,20 +301,20 @@ proc unstage_helper {txt paths} {
 		M? -
 		T? -
 		D? {
-			lappend pathList $path
+			lappend path_list $path
 			if {$path eq $current_diff_path} {
 				set after {reshow_diff;}
 			}
 		}
 		}
 	}
-	if {$pathList eq {}} {
+	if {$path_list eq {}} {
 		unlock_index
 	} else {
 		update_indexinfo \
 			$txt \
-			$pathList \
-			[concat $after [list ui_ready]]
+			$path_list \
+			[concat $after {ui_ready;}]
 	}
 }
 
@@ -305,7 +337,7 @@ proc add_helper {txt paths} {
 
 	if {![lock_index begin-update]} return
 
-	set pathList [list]
+	set path_list [list]
 	set after {}
 	foreach path $paths {
 		switch -glob -- [lindex $file_states($path) 0] {
@@ -321,20 +353,20 @@ proc add_helper {txt paths} {
 		?M -
 		?D -
 		?T {
-			lappend pathList $path
+			lappend path_list $path
 			if {$path eq $current_diff_path} {
 				set after {reshow_diff;}
 			}
 		}
 		}
 	}
-	if {$pathList eq {}} {
+	if {$path_list eq {}} {
 		unlock_index
 	} else {
 		update_index \
 			$txt \
-			$pathList \
-			[concat $after {ui_status [mc "Ready to commit."]}]
+			$path_list \
+			[concat $after {ui_status [mc "Ready to commit."];}]
 	}
 }
 
@@ -388,66 +420,303 @@ proc do_add_all {} {
 	add_helper [mc "Adding all changed files"] $paths
 }
 
+# Copied from TclLib package "lambda".
+proc lambda {arguments body args} {
+	return [list ::apply [list $arguments $body] {*}$args]
+}
+
 proc revert_helper {txt paths} {
 	global file_states current_diff_path
 
 	if {![lock_index begin-update]} return
 
-	set pathList [list]
-	set after {}
+	# Common "after" functionality that waits until multiple asynchronous
+	# operations are complete (by waiting for them to activate their notes
+	# on the chord).
+	#
+	# The asynchronous operations are each indicated below by a comment
+	# before the code block that starts the async operation.
+	set after_chord [SimpleChord::new {
+		if {[string trim $err] != ""} {
+			rescan_on_error $err
+		} else {
+			unlock_index
+			if {$should_reshow_diff} { reshow_diff }
+			ui_ready
+		}
+	}]
+
+	$after_chord eval { set should_reshow_diff 0 }
+
+	# This function captures an error for processing when after_chord is
+	# completed. (The chord is curried into the lambda function.)
+	set capture_error [lambda \
+		{chord error} \
+		{ $chord eval [list set err $error] } \
+		$after_chord]
+
+	# We don't know how many notes we're going to create (it's dynamic based
+	# on conditional paths below), so create a common note that will delay
+	# the chord's completion until we activate it, and then activate it
+	# after all the other notes have been created.
+	set after_common_note [$after_chord add_note]
+
+	set path_list [list]
+	set untracked_list [list]
+
 	foreach path $paths {
 		switch -glob -- [lindex $file_states($path) 0] {
 		U? {continue}
+		?O {
+			lappend untracked_list $path
+		}
 		?M -
 		?T -
 		?D {
-			lappend pathList $path
+			lappend path_list $path
 			if {$path eq $current_diff_path} {
-				set after {reshow_diff;}
+				$after_chord eval { set should_reshow_diff 1 }
 			}
 		}
 		}
 	}
 
+	set path_cnt [llength $path_list]
+	set untracked_cnt [llength $untracked_list]
+
+	# Asynchronous operation: revert changes by checking them out afresh
+	# from the index.
+	if {$path_cnt > 0} {
+		# Split question between singular and plural cases, because
+		# such distinction is needed in some languages. Previously, the
+		# code used "Revert changes in" for both, but that can't work
+		# in languages where 'in' must be combined with word from
+		# rest of string (in different way for both cases of course).
+		#
+		# FIXME: Unfortunately, even that isn't enough in some languages
+		# as they have quite complex plural-form rules. Unfortunately,
+		# msgcat doesn't seem to support that kind of string
+		# translation.
+		#
+		if {$path_cnt == 1} {
+			set query [mc \
+				"Revert changes in file %s?" \
+				[short_path [lindex $path_list]] \
+				]
+		} else {
+			set query [mc \
+				"Revert changes in these %i files?" \
+				$path_cnt]
+		}
 
-	# Split question between singular and plural cases, because
-	# such distinction is needed in some languages. Previously, the
-	# code used "Revert changes in" for both, but that can't work
-	# in languages where 'in' must be combined with word from
-	# rest of string (in different way for both cases of course).
-	#
-	# FIXME: Unfortunately, even that isn't enough in some languages
-	# as they have quite complex plural-form rules. Unfortunately,
-	# msgcat doesn't seem to support that kind of string translation.
-	#
-	set n [llength $pathList]
-	if {$n == 0} {
-		unlock_index
-		return
-	} elseif {$n == 1} {
-		set query [mc "Revert changes in file %s?" [short_path [lindex $pathList]]]
-	} else {
-		set query [mc "Revert changes in these %i files?" $n]
+		set reply [tk_dialog \
+			.confirm_revert \
+			"[appname] ([reponame])" \
+			"$query
+
+[mc "Any unstaged changes will be permanently lost by the revert."]" \
+			question \
+			1 \
+			[mc "Do Nothing"] \
+			[mc "Revert Changes"] \
+			]
+
+		if {$reply == 1} {
+			set note [$after_chord add_note]
+			checkout_index \
+				$txt \
+				$path_list \
+				[list $note activate] \
+				$capture_error
+		}
+	}
+
+	# Asynchronous operation: Deletion of untracked files.
+	if {$untracked_cnt > 0} {
+		# Split question between singular and plural cases, because
+		# such distinction is needed in some languages.
+		#
+		# FIXME: Unfortunately, even that isn't enough in some languages
+		# as they have quite complex plural-form rules. Unfortunately,
+		# msgcat doesn't seem to support that kind of string
+		# translation.
+		#
+		if {$untracked_cnt == 1} {
+			set query [mc \
+				"Delete untracked file %s?" \
+				[short_path [lindex $untracked_list]] \
+				]
+		} else {
+			set query [mc \
+				"Delete these %i untracked files?" \
+				$untracked_cnt \
+				]
+		}
+
+		set reply [tk_dialog \
+			.confirm_revert \
+			"[appname] ([reponame])" \
+			"$query
+
+[mc "Files will be permanently deleted."]" \
+			question \
+			1 \
+			[mc "Do Nothing"] \
+			[mc "Delete Files"] \
+			]
+
+		if {$reply == 1} {
+			$after_chord eval { set should_reshow_diff 1 }
+
+			set note [$after_chord add_note]
+			delete_files $untracked_list [list $note activate]
+		}
 	}
 
-	set reply [tk_dialog \
-		.confirm_revert \
-		"[appname] ([reponame])" \
-		"$query
+	# Activate the common note. If no other notes were created, this
+	# completes the chord. If other notes were created, then this common
+	# note prevents a race condition where the chord might complete early.
+	$after_common_note activate
+}
 
-[mc "Any unstaged changes will be permanently lost by the revert."]" \
-		question \
-		1 \
-		[mc "Do Nothing"] \
-		[mc "Revert Changes"] \
-		]
-	if {$reply == 1} {
-		checkout_index \
-			$txt \
-			$pathList \
-			[concat $after [list ui_ready]]
+# Delete all of the specified files, performing deletion in batches to allow the
+# UI to remain responsive and updated.
+proc delete_files {path_list after} {
+	# Enable progress bar status updates
+	set status_bar_operation [$::main_status \
+		start \
+		[mc "Deleting"] \
+		[mc "files"]]
+
+	set path_index 0
+	set deletion_errors [list]
+	set batch_size 50
+
+	delete_helper \
+		$path_list \
+		$path_index \
+		$deletion_errors \
+		$batch_size \
+		$status_bar_operation \
+		$after
+}
+
+# Helper function to delete a list of files in batches. Each call deletes one
+# batch of files, and then schedules a call for the next batch after any UI
+# messages have been processed.
+proc delete_helper {path_list path_index deletion_errors batch_size \
+	status_bar_operation after} {
+	global file_states
+
+	set path_cnt [llength $path_list]
+
+	set batch_remaining $batch_size
+
+	while {$batch_remaining > 0} {
+		if {$path_index >= $path_cnt} { break }
+
+		set path [lindex $path_list $path_index]
+
+		set deletion_failed [catch {file delete -- $path} deletion_error]
+
+		if {$deletion_failed} {
+			lappend deletion_errors [list "$deletion_error"]
+		} else {
+			remove_empty_directories [file dirname $path]
+
+			# Don't assume the deletion worked. Remove the file from
+			# the UI, but only if it no longer exists.
+			if {![path_exists $path]} {
+				unset file_states($path)
+				display_file $path __
+			}
+		}
+
+		incr path_index 1
+		incr batch_remaining -1
+	}
+
+	# Update the progress bar to indicate that this batch has been
+	# completed. The update will be visible when this procedure returns
+	# and allows the UI thread to process messages.
+	$status_bar_operation update $path_index $path_cnt
+
+	if {$path_index < $path_cnt} {
+		# The Tcler's Wiki lists this as the best practice for keeping
+		# a UI active and processing messages during a long-running
+		# operation.
+
+		after idle [list after 0 [list \
+			delete_helper \
+			$path_list \
+			$path_index \
+			$deletion_errors \
+			$batch_size \
+			$status_bar_operation \
+			$after
+			]]
 	} else {
-		unlock_index
+		# Finish the status bar operation.
+		$status_bar_operation stop
+
+		# Report error, if any, based on how many deletions failed.
+		set deletion_error_cnt [llength $deletion_errors]
+
+		if {($deletion_error_cnt > 0)
+		 && ($deletion_error_cnt <= [MAX_VERBOSE_FILES_IN_DELETION_ERROR])} {
+			set error_text [mc "Encountered errors deleting files:\n"]
+
+			foreach deletion_error $deletion_errors {
+				append error_text "* [lindex $deletion_error 0]\n"
+			}
+
+			error_popup $error_text
+		} elseif {$deletion_error_cnt == $path_cnt} {
+			error_popup [mc \
+				"None of the %d selected files could be deleted." \
+				$path_cnt \
+				]
+		} elseif {$deletion_error_cnt > 1} {
+			error_popup [mc \
+				"%d of the %d selected files could not be deleted." \
+				$deletion_error_cnt \
+				$path_cnt \
+				]
+		}
+
+		uplevel #0 $after
+	}
+}
+
+proc MAX_VERBOSE_FILES_IN_DELETION_ERROR {} { return 10; }
+
+# This function is from the TCL documentation:
+#
+#   https://wiki.tcl-lang.org/page/file+exists
+#
+# [file exists] returns false if the path does exist but is a symlink to a path
+# that doesn't exist. This proc returns true if the path exists, regardless of
+# whether it is a symlink and whether it is broken.
+proc path_exists {name} {
+	expr {![catch {file lstat $name finfo}]}
+}
+
+# Remove as many empty directories as we can starting at the specified path,
+# walking up the directory tree. If we encounter a directory that is not
+# empty, or if a directory deletion fails, then we stop the operation and
+# return to the caller. Even if this procedure fails to delete any
+# directories at all, it does not report failure.
+proc remove_empty_directories {directory_path} {
+	set parent_path [file dirname $directory_path]
+
+	while {$parent_path != $directory_path} {
+		set contents [glob -nocomplain -dir $directory_path *]
+
+		if {[llength $contents] > 0} { break }
+		if {[catch {file delete -- $directory_path}]} { break }
+
+		set directory_path $parent_path
+		set parent_path [file dirname $directory_path]
 	}
 }
 
@@ -466,19 +735,19 @@ proc do_revert_selection {} {
 }
 
 proc do_select_commit_type {} {
-	global commit_type selected_commit_type
+	global commit_type commit_type_is_amend
 
-	if {$selected_commit_type eq {new}
+	if {$commit_type_is_amend == 0
 		&& [string match amend* $commit_type]} {
 		create_new_commit
-	} elseif {$selected_commit_type eq {amend}
+	} elseif {$commit_type_is_amend == 1
 		&& ![string match amend* $commit_type]} {
 		load_last_commit
 
 		# The amend request was rejected...
 		#
 		if {![string match amend* $commit_type]} {
-			set selected_commit_type new
+			set commit_type_is_amend 0
 		}
 	}
 }
diff --git a/third_party/git/git-gui/lib/merge.tcl b/third_party/git/git-gui/lib/merge.tcl
index 9f253db5b37e..664803cf3fd1 100644
--- a/third_party/git/git-gui/lib/merge.tcl
+++ b/third_party/git/git-gui/lib/merge.tcl
@@ -241,23 +241,27 @@ Continue with resetting the current changes?"]
 	if {[ask_popup $op_question] eq {yes}} {
 		set fd [git_read --stderr read-tree --reset -u -v HEAD]
 		fconfigure $fd -blocking 0 -translation binary
-		fileevent $fd readable [namespace code [list _reset_wait $fd]]
-		$::main_status start [mc "Aborting"] [mc "files reset"]
+		set status_bar_operation [$::main_status \
+			start \
+			[mc "Aborting"] \
+			[mc "files reset"]]
+		fileevent $fd readable [namespace code [list \
+			_reset_wait $fd $status_bar_operation]]
 	} else {
 		unlock_index
 	}
 }
 
-proc _reset_wait {fd} {
+proc _reset_wait {fd status_bar_operation} {
 	global ui_comm
 
-	$::main_status update_meter [read $fd]
+	$status_bar_operation update_meter [read $fd]
 
 	fconfigure $fd -blocking 1
 	if {[eof $fd]} {
 		set fail [catch {close $fd} err]
-		$::main_status stop
 		unlock_index
+		$status_bar_operation stop
 
 		$ui_comm delete 0.0 end
 		$ui_comm edit modified false
diff --git a/third_party/git/git-gui/lib/mergetool.tcl b/third_party/git/git-gui/lib/mergetool.tcl
index 120bc4064b6f..e688b016ef6c 100644
--- a/third_party/git/git-gui/lib/mergetool.tcl
+++ b/third_party/git/git-gui/lib/mergetool.tcl
@@ -59,7 +59,7 @@ proc merge_add_resolution {path} {
 	update_index \
 		[mc "Adding resolution for %s" [short_path $path]] \
 		[list $path] \
-		[concat $after [list ui_ready]]
+		[concat $after {ui_ready;}]
 }
 
 proc merge_force_stage {stage} {
diff --git a/third_party/git/git-gui/lib/status_bar.tcl b/third_party/git/git-gui/lib/status_bar.tcl
index 02111a1742f9..d32b14142ff8 100644
--- a/third_party/git/git-gui/lib/status_bar.tcl
+++ b/third_party/git/git-gui/lib/status_bar.tcl
@@ -1,16 +1,42 @@
 # git-gui status bar mega-widget
 # Copyright (C) 2007 Shawn Pearce
 
+# The status_bar class manages the entire status bar. It is possible for
+# multiple overlapping asynchronous operations to want to display status
+# simultaneously. Each one receives a status_bar_operation when it calls the
+# start method, and the status bar combines all active operations into the
+# line of text it displays. Most of the time, there will be at most one
+# ongoing operation.
+#
+# Note that the entire status bar can be either in single-line or two-line
+# mode, depending on the constructor. Multiple active operations are only
+# supported for single-line status bars.
+
 class status_bar {
 
+field allow_multiple ; # configured at construction
+
 field w         ; # our own window path
 field w_l       ; # text widget we draw messages into
 field w_c       ; # canvas we draw a progress bar into
 field c_pack    ; # script to pack the canvas with
-field status  {}; # single line of text we show
-field prefix  {}; # text we format into status
-field units   {}; # unit of progress
-field meter   {}; # current core git progress meter (if active)
+
+field baseline_text   ; # text to show if there are no operations
+field status_bar_text ; # combined text for all operations
+
+field operations ; # list of current ongoing operations
+
+# The status bar can display a progress bar, updated when consumers call the
+# update method on their status_bar_operation. When there are multiple
+# operations, the status bar shows the combined status of all operations.
+#
+# When an overlapping operation completes, the progress bar is going to
+# abruptly have one fewer operation in the calculation, causing a discontinuity.
+# Therefore, whenever an operation completes, if it is not the last operation,
+# this counter is increased, and the progress bar is calculated as though there
+# were still another operation at 100%. When the last operation completes, this
+# is reset to 0.
+field completed_operation_count
 
 constructor new {path} {
 	global use_ttk NS
@@ -18,12 +44,19 @@ constructor new {path} {
 	set w_l $w.l
 	set w_c $w.c
 
+	# Standard single-line status bar: Permit overlapping operations
+	set allow_multiple 1
+
+	set baseline_text ""
+	set operations [list]
+	set completed_operation_count 0
+
 	${NS}::frame $w
 	if {!$use_ttk} {
 		$w configure -borderwidth 1 -relief sunken
 	}
 	${NS}::label $w_l \
-		-textvariable @status \
+		-textvariable @status_bar_text \
 		-anchor w \
 		-justify left
 	pack $w_l -side left
@@ -44,9 +77,16 @@ constructor two_line {path} {
 	set w_l $w.l
 	set w_c $w.c
 
+	# Two-line status bar: Only one ongoing operation permitted.
+	set allow_multiple 0
+
+	set baseline_text ""
+	set operations [list]
+	set completed_operation_count 0
+
 	${NS}::frame $w
 	${NS}::label $w_l \
-		-textvariable @status \
+		-textvariable @status_bar_text \
 		-anchor w \
 		-justify left
 	pack $w_l -anchor w -fill x
@@ -56,7 +96,7 @@ constructor two_line {path} {
 	return $this
 }
 
-method start {msg uds} {
+method ensure_canvas {} {
 	if {[winfo exists $w_c]} {
 		$w_c coords bar 0 0 0 20
 	} else {
@@ -68,31 +108,170 @@ method start {msg uds} {
 		$w_c create rectangle 0 0 0 20 -tags bar -fill navy
 		eval $c_pack
 	}
+}
+
+method show {msg} {
+	$this ensure_canvas
+	set baseline_text $msg
+	$this refresh
+}
+
+method start {msg {uds {}}} {
+	set baseline_text ""
+
+	if {!$allow_multiple && [llength $operations]} {
+		return [lindex $operations 0]
+	}
+
+	$this ensure_canvas
+
+	set operation [status_bar_operation::new $this $msg $uds]
+
+	lappend operations $operation
+
+	$this refresh
+
+	return $operation
+}
+
+method refresh {} {
+	set new_text ""
+
+	set total [expr $completed_operation_count * 100]
+	set have $total
+
+	foreach operation $operations {
+		if {$new_text != ""} {
+			append new_text " / "
+		}
+
+		append new_text [$operation get_status]
+
+		set total [expr $total + 100]
+		set have [expr $have + [$operation get_progress]]
+	}
+
+	if {$new_text == ""} {
+		set new_text $baseline_text
+	}
+
+	set status_bar_text $new_text
+
+	if {[winfo exists $w_c]} {
+		set pixel_width 0
+		if {$have > 0} {
+			set pixel_width [expr {[winfo width $w_c] * $have / $total}]
+		}
+
+		$w_c coords bar 0 0 $pixel_width 20
+	}
+}
+
+method stop {operation stop_msg} {
+	set idx [lsearch $operations $operation]
+
+	if {$idx >= 0} {
+		set operations [lreplace $operations $idx $idx]
+		set completed_operation_count [expr \
+			$completed_operation_count + 1]
+
+		if {[llength $operations] == 0} {
+			set completed_operation_count 0
+
+			destroy $w_c
+			if {$stop_msg ne {}} {
+				set baseline_text $stop_msg
+			}
+		}
+
+		$this refresh
+	}
+}
+
+method stop_all {{stop_msg {}}} {
+	# This makes the operation's call to stop a no-op.
+	set operations_copy $operations
+	set operations [list]
+
+	foreach operation $operations_copy {
+		$operation stop
+	}
+
+	if {$stop_msg ne {}} {
+		set baseline_text $stop_msg
+	}
+
+	$this refresh
+}
+
+method _delete {current} {
+	if {$current eq $w} {
+		delete_this
+	}
+}
+
+}
+
+# The status_bar_operation class tracks a single consumer's ongoing status bar
+# activity, with the context that there are a few situations where multiple
+# overlapping asynchronous operations might want to display status information
+# simultaneously. Instances of status_bar_operation are created by calling
+# start on the status_bar, and when the caller is done with its stauts bar
+# operation, it calls stop on the operation.
+
+class status_bar_operation {
+
+field status_bar; # reference back to the status_bar that owns this object
+
+field is_active;
+
+field status   {}; # single line of text we show
+field progress {}; # current progress (0 to 100)
+field prefix   {}; # text we format into status
+field units    {}; # unit of progress
+field meter    {}; # current core git progress meter (if active)
+
+constructor new {owner msg uds} {
+	set status_bar $owner
 
 	set status $msg
+	set progress 0
 	set prefix $msg
 	set units  $uds
 	set meter  {}
+
+	set is_active 1
+
+	return $this
 }
 
+method get_is_active {} { return $is_active }
+method get_status {} { return $status }
+method get_progress {} { return $progress }
+
 method update {have total} {
-	set pdone 0
-	set cdone 0
+	if {!$is_active} { return }
+
+	set progress 0
+
 	if {$total > 0} {
-		set pdone [expr {100 * $have / $total}]
-		set cdone [expr {[winfo width $w_c] * $have / $total}]
+		set progress [expr {100 * $have / $total}]
 	}
 
 	set prec [string length [format %i $total]]
+
 	set status [mc "%s ... %*i of %*i %s (%3i%%)" \
 		$prefix \
 		$prec $have \
 		$prec $total \
-		$units $pdone]
-	$w_c coords bar 0 0 $cdone 20
+		$units $progress]
+
+	$status_bar refresh
 }
 
 method update_meter {buf} {
+	if {!$is_active} { return }
+
 	append meter $buf
 	set r [string last "\r" $meter]
 	if {$r == -1} {
@@ -109,23 +288,25 @@ method update_meter {buf} {
 	}
 }
 
-method stop {{msg {}}} {
-	destroy $w_c
-	if {$msg ne {}} {
-		set status $msg
+method stop {{stop_msg {}}} {
+	if {$is_active} {
+		set is_active 0
+		$status_bar stop $this $stop_msg
 	}
 }
 
-method show {msg {test {}}} {
-	if {$test eq {} || $status eq $test} {
-		set status $msg
-	}
+method restart {msg} {
+	if {!$is_active} { return }
+
+	set status $msg
+	set prefix $msg
+	set meter {}
+	$status_bar refresh
 }
 
-method _delete {current} {
-	if {$current eq $w} {
-		delete_this
-	}
+method _delete {} {
+	stop
+	delete_this
 }
 
 }
diff --git a/third_party/git/git-gui/lib/themed.tcl b/third_party/git/git-gui/lib/themed.tcl
index 88b3119a7506..83e3ac795f38 100644
--- a/third_party/git/git-gui/lib/themed.tcl
+++ b/third_party/git/git-gui/lib/themed.tcl
@@ -1,6 +1,44 @@
 # Functions for supporting the use of themed Tk widgets in git-gui.
 # Copyright (C) 2009 Pat Thoyts <patthoyts@users.sourceforge.net>
 
+
+namespace eval color {
+	# Variable colors
+	# Preffered way to set widget colors is using add_option.
+	# In some cases, like with tags in_diff/in_sel, we use these colors.
+	variable select_bg		lightgray
+	variable select_fg		black
+
+	proc sync_with_theme {} {
+		set base_bg		[ttk::style lookup . -background]
+		set base_fg		[ttk::style lookup . -foreground]
+		set text_bg		[ttk::style lookup Treeview -background]
+		set text_fg		[ttk::style lookup Treeview -foreground]
+		set select_bg	[ttk::style lookup Default -selectbackground]
+		set select_fg	[ttk::style lookup Default -selectforeground]
+
+		set color::select_bg $select_bg
+		set color::select_fg $select_fg
+
+		proc add_option {key val} {
+			option add $key $val widgetDefault
+		}
+		# Add options for plain Tk widgets
+		# Using `option add` instead of tk_setPalette to avoid unintended
+		# consequences.
+		if {![is_MacOSX]} {
+			add_option *Menu.Background $base_bg
+			add_option *Menu.Foreground $base_fg
+			add_option *Menu.activeBackground $select_bg
+			add_option *Menu.activeForeground $select_fg
+		}
+		add_option *Text.Background $text_bg
+		add_option *Text.Foreground $text_fg
+		add_option *Text.HighlightBackground $base_bg
+		add_option *Text.HighlightColor $select_bg
+	}
+}
+
 proc ttk_get_current_theme {} {
 	# Handle either current Tk or older versions of 8.5
 	if {[catch {set theme [ttk::style theme use]}]} {