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/git-merge-base.txt

@@ -80,11 +80,9 @@ which is reachable from both 'A' and 'B' through the parent relationship.
 
 For example, with this topology:
 
-....
-	 o---o---o---B
-	/
----o---1---o---o---o---A
-....
+	         o---o---o---B
+	        /
+	---o---1---o---o---o---A
 
 the merge base between 'A' and 'B' is '1'.
 
@@ -92,25 +90,21 @@ Given three commits 'A', 'B' and 'C', `git merge-base A B C` will compute the
 merge base between 'A' and a hypothetical commit 'M', which is a merge
 between 'B' and 'C'.  For example, with this topology:
 
-....
-       o---o---o---o---C
-      /
-     /   o---o---o---B
-    /   /
----2---1---o---o---o---A
-....
+	       o---o---o---o---C
+	      /
+	     /   o---o---o---B
+	    /   /
+	---2---1---o---o---o---A
 
 the result of `git merge-base A B C` is '1'.  This is because the
 equivalent topology with a merge commit 'M' between 'B' and 'C' is:
 
 
-....
-       o---o---o---o---o
-      /                 \
-     /   o---o---o---o---M
-    /   /
----2---1---o---o---o---A
-....
+	       o---o---o---o---o
+	      /                 \
+	     /   o---o---o---o---M
+	    /   /
+	---2---1---o---o---o---A
 
 and the result of `git merge-base A M` is '1'.  Commit '2' is also a
 common ancestor between 'A' and 'M', but '1' is a better common ancestor,
@@ -122,13 +116,11 @@ the best common ancestor of all commits.
 When the history involves criss-cross merges, there can be more than one
 'best' common ancestor for two commits.  For example, with this topology:
 
-....
----1---o---A
-    \ /
-     X
-    / \
----2---o---o---B
-....
+	---1---o---A
+	    \ /
+	     X
+	    / \
+	---2---o---o---B
 
 both '1' and '2' are merge-bases of A and B.  Neither one is better than
 the other (both are 'best' merge bases).  When the `--all` option is not given,
@@ -139,22 +131,18 @@ and B is (or at least used to be) to compute the merge base between
 A and B, and check if it is the same as A, in which case, A is an
 ancestor of B.  You will see this idiom used often in older scripts.
 
-....
-A=$(git rev-parse --verify A)
-if test "$A" = "$(git merge-base A B)"
-then
-	... A is an ancestor of B ...
-fi
-....
+	A=$(git rev-parse --verify A)
+	if test "$A" = "$(git merge-base A B)"
+	then
+		... A is an ancestor of B ...
+	fi
 
 In modern git, you can say this in a more direct way:
 
-....
-if git merge-base --is-ancestor A B
-then
-	... A is an ancestor of B ...
-fi
-....
+	if git merge-base --is-ancestor A B
+	then
+		... A is an ancestor of B ...
+	fi
 
 instead.
 
@@ -166,15 +154,13 @@ topic origin/master`, the history of remote-tracking branch
 `origin/master` may have been rewound and rebuilt, leading to a
 history of this shape:
 
-....
-		 o---B2
-		/
----o---o---B1--o---o---o---B (origin/master)
-	\
-	 B0
-	  \
-	   D0---D1---D (topic)
-....
+	                 o---B2
+	                /
+	---o---o---B1--o---o---o---B (origin/master)
+	        \
+	         B0
+	          \
+	           D0---D1---D (topic)
 
 where `origin/master` used to point at commits B0, B1, B2 and now it
 points at B, and your `topic` branch was started on top of it back
@@ -207,15 +193,13 @@ will find B0, and
 will replay D0, D1 and D on top of B to create a new history of this
 shape:
 
-....
-		 o---B2
-		/
----o---o---B1--o---o---o---B (origin/master)
-	\                   \
-	 B0                  D0'--D1'--D' (topic - updated)
-	  \
-	   D0---D1---D (topic - old)
-....
+			 o---B2
+			/
+	---o---o---B1--o---o---o---B (origin/master)
+		\                   \
+		 B0                  D0'--D1'--D' (topic - updated)
+		  \
+		   D0---D1---D (topic - old)
 
 A caveat is that older reflog entries in your repository may be
 expired by `git gc`.  If B0 no longer appears in the reflog of the