revert(3p/git): Revert merge of git upstream at v2.26.2

This causes cgit to serve error pages, which is undesirable.

This reverts commit 5229c9b232, reversing
changes made to f2b211131f.

third_party/git/Documentation/SubmittingPatches

@@ -142,25 +142,19 @@ archive, summarize the relevant points of the discussion.
 
 [[commit-reference]]
 If you want to reference a previous commit in the history of a stable
-branch, use the format "abbreviated hash (subject, date)", like this:
+branch, use the format "abbreviated sha1 (subject, date)",
+with the subject enclosed in a pair of double-quotes, like this:
 
 ....
-	Commit f86a374 (pack-bitmap.c: fix a memleak, 2015-03-30)
+	Commit f86a374 ("pack-bitmap.c: fix a memleak", 2015-03-30)
 	noticed that ...
 ....
 
 The "Copy commit summary" command of gitk can be used to obtain this
-format (with the subject enclosed in a pair of double-quotes), or this
-invocation of `git show`:
+format, or this invocation of `git show`:
 
 ....
-	git show -s --pretty=reference <commit>
-....
-
-or, on an older version of Git without support for --pretty=reference:
-
-....
-	git show -s --date=short --pretty='format:%h (%s, %ad)' <commit>
+	git show -s --date=short --pretty='format:%h ("%s", %ad)' <commit>
 ....
 
 [[git-tools]]
@@ -378,9 +372,9 @@ such as "Thanks-to:", "Based-on-patch-by:", or "Mentored-by:".
 Some parts of the system have dedicated maintainers with their own
 repositories.
 
-- `git-gui/` comes from git-gui project, maintained by Pratyush Yadav:
+- `git-gui/` comes from git-gui project, maintained by Pat Thoyts:
 
-	https://github.com/prati0100/git-gui.git
+	git://repo.or.cz/git-gui.git
 
 - `gitk-git/` comes from Paul Mackerras's gitk project: