merge(third_party/git): Merge squashed git subtree at v2.23.0 r/373

Merge commit '1b593e1ea4d2af0f6444d9a7788d5d99abd6fde5' as 'third_party/git'

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+SPECIFYING REVISIONS
+--------------------
+
+A revision parameter '<rev>' typically, but not necessarily, names a
+commit object.  It uses what is called an 'extended SHA-1'
+syntax.  Here are various ways to spell object names.  The
+ones listed near the end of this list name trees and
+blobs contained in a commit.
+
+NOTE: This document shows the "raw" syntax as seen by git. The shell
+and other UIs might require additional quoting to protect special
+characters and to avoid word splitting.
+
+'<sha1>', e.g. 'dae86e1950b1277e545cee180551750029cfe735', 'dae86e'::
+  The full SHA-1 object name (40-byte hexadecimal string), or
+  a leading substring that is unique within the repository.
+  E.g. dae86e1950b1277e545cee180551750029cfe735 and dae86e both
+  name the same commit object if there is no other object in
+  your repository whose object name starts with dae86e.
+
+'<describeOutput>', e.g. 'v1.7.4.2-679-g3bee7fb'::
+  Output from `git describe`; i.e. a closest tag, optionally
+  followed by a dash and a number of commits, followed by a dash, a
+  'g', and an abbreviated object name.
+
+'<refname>', e.g. 'master', 'heads/master', 'refs/heads/master'::
+  A symbolic ref name.  E.g. 'master' typically means the commit
+  object referenced by 'refs/heads/master'.  If you
+  happen to have both 'heads/master' and 'tags/master', you can
+  explicitly say 'heads/master' to tell Git which one you mean.
+  When ambiguous, a '<refname>' is disambiguated by taking the
+  first match in the following rules:
+
+  . If '$GIT_DIR/<refname>' exists, that is what you mean (this is usually
+    useful only for `HEAD`, `FETCH_HEAD`, `ORIG_HEAD`, `MERGE_HEAD`
+    and `CHERRY_PICK_HEAD`);
+
+  . otherwise, 'refs/<refname>' if it exists;
+
+  . otherwise, 'refs/tags/<refname>' if it exists;
+
+  . otherwise, 'refs/heads/<refname>' if it exists;
+
+  . otherwise, 'refs/remotes/<refname>' if it exists;
+
+  . otherwise, 'refs/remotes/<refname>/HEAD' if it exists.
++
+`HEAD` names the commit on which you based the changes in the working tree.
+`FETCH_HEAD` records the branch which you fetched from a remote repository
+with your last `git fetch` invocation.
+`ORIG_HEAD` is created by commands that move your `HEAD` in a drastic
+way, to record the position of the `HEAD` before their operation, so that
+you can easily change the tip of the branch back to the state before you ran
+them.
+`MERGE_HEAD` records the commit(s) which you are merging into your branch
+when you run `git merge`.
+`CHERRY_PICK_HEAD` records the commit which you are cherry-picking
+when you run `git cherry-pick`.
++
+Note that any of the 'refs/*' cases above may come either from
+the `$GIT_DIR/refs` directory or from the `$GIT_DIR/packed-refs` file.
+While the ref name encoding is unspecified, UTF-8 is preferred as
+some output processing may assume ref names in UTF-8.
+
+'@'::
+  '@' alone is a shortcut for `HEAD`.
+
+'[<refname>]@{<date>}', e.g. 'master@\{yesterday\}', 'HEAD@{5 minutes ago}'::
+  A ref followed by the suffix '@' with a date specification
+  enclosed in a brace
+  pair (e.g. '\{yesterday\}', '{1 month 2 weeks 3 days 1 hour 1
+  second ago}' or '{1979-02-26 18:30:00}') specifies the value
+  of the ref at a prior point in time.  This suffix may only be
+  used immediately following a ref name and the ref must have an
+  existing log ('$GIT_DIR/logs/<ref>'). Note that this looks up the state
+  of your *local* ref at a given time; e.g., what was in your local
+  'master' branch last week. If you want to look at commits made during
+  certain times, see `--since` and `--until`.
+
+'<refname>@{<n>}', e.g. 'master@\{1\}'::
+  A ref followed by the suffix '@' with an ordinal specification
+  enclosed in a brace pair (e.g. '\{1\}', '\{15\}') specifies
+  the n-th prior value of that ref.  For example 'master@\{1\}'
+  is the immediate prior value of 'master' while 'master@\{5\}'
+  is the 5th prior value of 'master'. This suffix may only be used
+  immediately following a ref name and the ref must have an existing
+  log ('$GIT_DIR/logs/<refname>').
+
+'@{<n>}', e.g. '@\{1\}'::
+  You can use the '@' construct with an empty ref part to get at a
+  reflog entry of the current branch. For example, if you are on
+  branch 'blabla' then '@\{1\}' means the same as 'blabla@\{1\}'.
+
+'@{-<n>}', e.g. '@{-1}'::
+  The construct '@{-<n>}' means the <n>th branch/commit checked out
+  before the current one.
+
+'[<branchname>]@\{upstream\}', e.g. 'master@\{upstream\}', '@\{u\}'::
+  The suffix '@\{upstream\}' to a branchname (short form '<branchname>@\{u\}')
+  refers to the branch that the branch specified by branchname is set to build on
+  top of (configured with `branch.<name>.remote` and
+  `branch.<name>.merge`).  A missing branchname defaults to the
+  current one. These suffixes are also accepted when spelled in uppercase, and
+  they mean the same thing no matter the case.
+
+'[<branchname>]@\{push\}', e.g. 'master@\{push\}', '@\{push\}'::
+  The suffix '@\{push}' reports the branch "where we would push to" if
+  `git push` were run while `branchname` was checked out (or the current
+  `HEAD` if no branchname is specified). Since our push destination is
+  in a remote repository, of course, we report the local tracking branch
+  that corresponds to that branch (i.e., something in `refs/remotes/`).
++
+Here's an example to make it more clear:
++
+------------------------------
+$ git config push.default current
+$ git config remote.pushdefault myfork
+$ git switch -c mybranch origin/master
+
+$ git rev-parse --symbolic-full-name @{upstream}
+refs/remotes/origin/master
+
+$ git rev-parse --symbolic-full-name @{push}
+refs/remotes/myfork/mybranch
+------------------------------
++
+Note in the example that we set up a triangular workflow, where we pull
+from one location and push to another. In a non-triangular workflow,
+'@\{push}' is the same as '@\{upstream}', and there is no need for it.
++
+This suffix is also accepted when spelled in uppercase, and means the same
+thing no matter the case.
+
+'<rev>{caret}[<n>]', e.g. 'HEAD{caret}, v1.5.1{caret}0'::
+  A suffix '{caret}' to a revision parameter means the first parent of
+  that commit object.  '{caret}<n>' means the <n>th parent (i.e.
+  '<rev>{caret}'
+  is equivalent to '<rev>{caret}1').  As a special rule,
+  '<rev>{caret}0' means the commit itself and is used when '<rev>' is the
+  object name of a tag object that refers to a commit object.
+
+'<rev>{tilde}[<n>]', e.g. 'HEAD{tilde}, master{tilde}3'::
+  A suffix '{tilde}' to a revision parameter means the first parent of
+  that commit object.
+  A suffix '{tilde}<n>' to a revision parameter means the commit
+  object that is the <n>th generation ancestor of the named
+  commit object, following only the first parents.  I.e. '<rev>{tilde}3' is
+  equivalent to '<rev>{caret}{caret}{caret}' which is equivalent to
+  '<rev>{caret}1{caret}1{caret}1'.  See below for an illustration of
+  the usage of this form.
+
+'<rev>{caret}{<type>}', e.g. 'v0.99.8{caret}\{commit\}'::
+  A suffix '{caret}' followed by an object type name enclosed in
+  brace pair means dereference the object at '<rev>' recursively until
+  an object of type '<type>' is found or the object cannot be
+  dereferenced anymore (in which case, barf).
+  For example, if '<rev>' is a commit-ish, '<rev>{caret}\{commit\}'
+  describes the corresponding commit object.
+  Similarly, if '<rev>' is a tree-ish, '<rev>{caret}\{tree\}'
+  describes the corresponding tree object.
+  '<rev>{caret}0'
+  is a short-hand for '<rev>{caret}\{commit\}'.
++
+'<rev>{caret}\{object\}' can be used to make sure '<rev>' names an
+object that exists, without requiring '<rev>' to be a tag, and
+without dereferencing '<rev>'; because a tag is already an object,
+it does not have to be dereferenced even once to get to an object.
++
+'<rev>{caret}\{tag\}' can be used to ensure that '<rev>' identifies an
+existing tag object.
+
+'<rev>{caret}{}', e.g. 'v0.99.8{caret}{}'::
+  A suffix '{caret}' followed by an empty brace pair
+  means the object could be a tag,
+  and dereference the tag recursively until a non-tag object is
+  found.
+
+'<rev>{caret}{/<text>}', e.g. 'HEAD^{/fix nasty bug}'::
+  A suffix '{caret}' to a revision parameter, followed by a brace
+  pair that contains a text led by a slash,
+  is the same as the ':/fix nasty bug' syntax below except that
+  it returns the youngest matching commit which is reachable from
+  the '<rev>' before '{caret}'.
+
+':/<text>', e.g. ':/fix nasty bug'::
+  A colon, followed by a slash, followed by a text, names
+  a commit whose commit message matches the specified regular expression.
+  This name returns the youngest matching commit which is
+  reachable from any ref, including HEAD.
+  The regular expression can match any part of the
+  commit message. To match messages starting with a string, one can use
+  e.g. ':/^foo'. The special sequence ':/!' is reserved for modifiers to what
+  is matched. ':/!-foo' performs a negative match, while ':/!!foo' matches a
+  literal '!' character, followed by 'foo'. Any other sequence beginning with
+  ':/!' is reserved for now.
+  Depending on the given text, the shell's word splitting rules might
+  require additional quoting.
+
+'<rev>:<path>', e.g. 'HEAD:README', 'master:./README'::
+  A suffix ':' followed by a path names the blob or tree
+  at the given path in the tree-ish object named by the part
+  before the colon.
+  A path starting with './' or '../' is relative to the current working directory.
+  The given path will be converted to be relative to the working tree's root directory.
+  This is most useful to address a blob or tree from a commit or tree that has
+  the same tree structure as the working tree.
+
+':[<n>:]<path>', e.g. ':0:README', ':README'::
+  A colon, optionally followed by a stage number (0 to 3) and a
+  colon, followed by a path, names a blob object in the
+  index at the given path. A missing stage number (and the colon
+  that follows it) names a stage 0 entry. During a merge, stage
+  1 is the common ancestor, stage 2 is the target branch's version
+  (typically the current branch), and stage 3 is the version from
+  the branch which is being merged.
+
+Here is an illustration, by Jon Loeliger.  Both commit nodes B
+and C are parents of commit node A.  Parent commits are ordered
+left-to-right.
+
+........................................
+G   H   I   J
+ \ /     \ /
+  D   E   F
+   \  |  / \
+    \ | /   |
+     \|/    |
+      B     C
+       \   /
+        \ /
+         A
+........................................
+
+    A =      = A^0
+    B = A^   = A^1     = A~1
+    C = A^2  = A^2
+    D = A^^  = A^1^1   = A~2
+    E = B^2  = A^^2
+    F = B^3  = A^^3
+    G = A^^^ = A^1^1^1 = A~3
+    H = D^2  = B^^2    = A^^^2  = A~2^2
+    I = F^   = B^3^    = A^^3^
+    J = F^2  = B^3^2   = A^^3^2
+
+
+SPECIFYING RANGES
+-----------------
+
+History traversing commands such as `git log` operate on a set
+of commits, not just a single commit.
+
+For these commands,
+specifying a single revision, using the notation described in the
+previous section, means the set of commits `reachable` from the given
+commit.
+
+A commit's reachable set is the commit itself and the commits in
+its ancestry chain.
+
+
+Commit Exclusions
+~~~~~~~~~~~~~~~~~
+
+'{caret}<rev>' (caret) Notation::
+ To exclude commits reachable from a commit, a prefix '{caret}'
+ notation is used.  E.g. '{caret}r1 r2' means commits reachable
+ from 'r2' but exclude the ones reachable from 'r1' (i.e. 'r1' and
+ its ancestors).
+
+Dotted Range Notations
+~~~~~~~~~~~~~~~~~~~~~~
+
+The '..' (two-dot) Range Notation::
+ The '{caret}r1 r2' set operation appears so often that there is a shorthand
+ for it.  When you have two commits 'r1' and 'r2' (named according
+ to the syntax explained in SPECIFYING REVISIONS above), you can ask
+ for commits that are reachable from r2 excluding those that are reachable
+ from r1 by '{caret}r1 r2' and it can be written as 'r1..r2'.
+
+The '...' (three-dot) Symmetric Difference Notation::
+ A similar notation 'r1\...r2' is called symmetric difference
+ of 'r1' and 'r2' and is defined as
+ 'r1 r2 --not $(git merge-base --all r1 r2)'.
+ It is the set of commits that are reachable from either one of
+ 'r1' (left side) or 'r2' (right side) but not from both.
+
+In these two shorthand notations, you can omit one end and let it default to HEAD.
+For example, 'origin..' is a shorthand for 'origin..HEAD' and asks "What
+did I do since I forked from the origin branch?"  Similarly, '..origin'
+is a shorthand for 'HEAD..origin' and asks "What did the origin do since
+I forked from them?"  Note that '..' would mean 'HEAD..HEAD' which is an
+empty range that is both reachable and unreachable from HEAD.
+
+Other <rev>{caret} Parent Shorthand Notations
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+Three other shorthands exist, particularly useful for merge commits,
+for naming a set that is formed by a commit and its parent commits.
+
+The 'r1{caret}@' notation means all parents of 'r1'.
+
+The 'r1{caret}!' notation includes commit 'r1' but excludes all of its parents.
+By itself, this notation denotes the single commit 'r1'.
+
+The '<rev>{caret}-[<n>]' notation includes '<rev>' but excludes the <n>th
+parent (i.e. a shorthand for '<rev>{caret}<n>..<rev>'), with '<n>' = 1 if
+not given. This is typically useful for merge commits where you
+can just pass '<commit>{caret}-' to get all the commits in the branch
+that was merged in merge commit '<commit>' (including '<commit>'
+itself).
+
+While '<rev>{caret}<n>' was about specifying a single commit parent, these
+three notations also consider its parents. For example you can say
+'HEAD{caret}2{caret}@', however you cannot say 'HEAD{caret}@{caret}2'.
+
+Revision Range Summary
+----------------------
+
+'<rev>'::
+	Include commits that are reachable from <rev> (i.e. <rev> and its
+	ancestors).
+
+'{caret}<rev>'::
+	Exclude commits that are reachable from <rev> (i.e. <rev> and its
+	ancestors).
+
+'<rev1>..<rev2>'::
+	Include commits that are reachable from <rev2> but exclude
+	those that are reachable from <rev1>.  When either <rev1> or
+	<rev2> is omitted, it defaults to `HEAD`.
+
+'<rev1>\...<rev2>'::
+	Include commits that are reachable from either <rev1> or
+	<rev2> but exclude those that are reachable from both.  When
+	either <rev1> or <rev2> is omitted, it defaults to `HEAD`.
+
+'<rev>{caret}@', e.g. 'HEAD{caret}@'::
+  A suffix '{caret}' followed by an at sign is the same as listing
+  all parents of '<rev>' (meaning, include anything reachable from
+  its parents, but not the commit itself).
+
+'<rev>{caret}!', e.g. 'HEAD{caret}!'::
+  A suffix '{caret}' followed by an exclamation mark is the same
+  as giving commit '<rev>' and then all its parents prefixed with
+  '{caret}' to exclude them (and their ancestors).
+
+'<rev>{caret}-<n>', e.g. 'HEAD{caret}-, HEAD{caret}-2'::
+	Equivalent to '<rev>{caret}<n>..<rev>', with '<n>' = 1 if not
+	given.
+
+Here are a handful of examples using the Loeliger illustration above,
+with each step in the notation's expansion and selection carefully
+spelt out:
+
+....
+   Args   Expanded arguments    Selected commits
+   D                            G H D
+   D F                          G H I J D F
+   ^G D                         H D
+   ^D B                         E I J F B
+   ^D B C                       E I J F B C
+   C                            I J F C
+   B..C   = ^B C                C
+   B...C  = B ^F C              G H D E B C
+   B^-    = B^..B
+	  = ^B^1 B              E I J F B
+   C^@    = C^1
+	  = F                   I J F
+   B^@    = B^1 B^2 B^3
+	  = D E F               D G H E F I J
+   C^!    = C ^C^@
+	  = C ^C^1
+	  = C ^F                C
+   B^!    = B ^B^@
+	  = B ^B^1 ^B^2 ^B^3
+	  = B ^D ^E ^F          B
+   F^! D  = F ^I ^J D           G H D F
+....