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

Merge commit '1b593e1ea4' as 'third_party/git'

third_party/git/Documentation/RelNotes/1.5.4.6.txt

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+GIT v1.5.4.6 Release Notes
+==========================
+
+I personally do not think there is any reason anybody should want to
+run v1.5.4.X series these days, because 'master' version is always
+more stable than any tagged released version of git.
+
+This is primarily to futureproof "git-shell" to accept requests
+without a dash between "git" and subcommand name (e.g. "git
+upload-pack") which the newer client will start to make sometime in
+the future.
+
+Fixes since v1.5.4.5
+--------------------
+
+ * Command line option "-n" to "git-repack" was not correctly parsed.
+
+ * Error messages from "git-apply" when the patchfile cannot be opened
+   have been improved.
+
+ * Error messages from "git-bisect" when given nonsense revisions have
+   been improved.
+
+ * reflog syntax that uses time e.g. "HEAD@{10 seconds ago}:path" did not
+   stop parsing at the closing "}".
+
+ * "git rev-parse --symbolic-full-name ^master^2" printed solitary "^",
+   but it should print nothing.
+
+ * "git apply" did not enforce "match at the beginning" correctly.
+
+ * a path specification "a/b" in .gitattributes file should not match
+   "sub/a/b", but it did.
+
+ * "git log --date-order --topo-order" did not override the earlier
+   date-order with topo-order as expected.
+
+ * "git fast-export" did not export octopus merges correctly.
+
+ * "git archive --prefix=$path/" mishandled gitattributes.
+
+As usual, it also comes with many documentation fixes and clarifications.
+