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

1 files changed, 23 insertions, 1 deletions

diff --git a/third_party/git/Documentation/git-update-index.txt b/third_party/git/Documentation/git-update-index.txt
index 1c4d146a41ce..1489cb09a099 100644
--- a/third_party/git/Documentation/git-update-index.txt
+++ b/third_party/git/Documentation/git-update-index.txt
@@ -16,6 +16,7 @@ SYNOPSIS
 	     [--chmod=(+|-)x]
 	     [--[no-]assume-unchanged]
 	     [--[no-]skip-worktree]
+	     [--[no-]ignore-skip-worktree-entries]
 	     [--[no-]fsmonitor-valid]
 	     [--ignore-submodules]
 	     [--[no-]split-index]
@@ -113,6 +114,11 @@ you will need to handle the situation manually.
 	set and unset the "skip-worktree" bit for the paths. See
 	section "Skip-worktree bit" below for more information.
 
+
+--[no-]ignore-skip-worktree-entries::
+	Do not remove skip-worktree (AKA "index-only") entries even when
+	the `--remove` option was specified.
+
 --[no-]fsmonitor-valid::
 	When one of these flags is specified, the object name recorded
 	for the paths are not updated. Instead, these options
@@ -426,7 +432,7 @@ specified by the splitIndex.sharedIndexExpire config variable (see
 linkgit:git-config[1]).
 
 To avoid deleting a shared index file that is still used, its
-modification time is updated to the current time everytime a new split
+modification time is updated to the current time every time a new split
 index based on the shared index file is either created or read from.
 
 UNTRACKED CACHE
@@ -543,6 +549,22 @@ The untracked cache extension can be enabled by the
 `core.untrackedCache` configuration variable (see
 linkgit:git-config[1]).
 
+NOTES
+-----
+
+Users often try to use the assume-unchanged and skip-worktree bits
+to tell Git to ignore changes to files that are tracked.  This does not
+work as expected, since Git may still check working tree files against
+the index when performing certain operations.  In general, Git does not
+provide a way to ignore changes to tracked files, so alternate solutions
+are recommended.
+
+For example, if the file you want to change is some sort of config file,
+the repository can include a sample config file that can then be copied
+into the ignored name and modified.  The repository can even include a
+script to treat the sample file as a template, modifying and copying it
+automatically.
+
 SEE ALSO
 --------
 linkgit:git-config[1],