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/git-gui/lib/commit.tcl

@@ -333,7 +333,7 @@ proc commit_writetree {curHEAD msg_p} {
 proc commit_committree {fd_wt curHEAD msg_p} {
 	global HEAD PARENT MERGE_HEAD commit_type commit_author
 	global current_branch
-	global ui_comm commit_type_is_amend
+	global ui_comm selected_commit_type
 	global file_states selected_paths rescan_active
 	global repo_config
 	global env
@@ -467,8 +467,8 @@ A rescan will be automatically started now.
 
 	# -- Update in memory status
 	#
+	set selected_commit_type new
 	set commit_type normal
-	set commit_type_is_amend 0
 	set HEAD $cmt_id
 	set PARENT $cmt_id
 	set MERGE_HEAD [list]