[PATCH/RFC] rebase: new convenient option to edit a single commit

["Nguyễn Thái Ngọc Duy" <pclouds@gmail.com>]

I find myself often do "git rebase -i xxx" and replace one "pick" line
with "edit" to amend just one commit when I see something I don't like
in that commit. This happens often while cleaning up a series. This
automates the "replace" step so it sends me straight to that commit.

"commit --fixup" then "rebase --autosquash" would work too but I still
need to edit todo file to make it stop after squashing so I can test
that commit. So still extra steps.

Or is there a better way to do this?

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
---
 git-rebase--interactive.sh | 17 ++++++++++++++---
 git-rebase.sh              | 10 ++++++++++
 2 files changed, 24 insertions(+), 3 deletions(-)

diff --git a/git-rebase--interactive.sh b/git-rebase--interactive.sh
index d741b04..0988b5c 100644
--- a/git-rebase--interactive.sh
+++ b/git-rebase--interactive.sh
@@ -1027,9 +1027,20 @@ fi
 has_action "$todo" ||
 	die_abort "Nothing to do"
 
-cp "$todo" "$todo".backup
-git_sequence_editor "$todo" ||
-	die_abort "Could not execute editor"
+if test -n "$edit_one"
+then
+	edit_one="`git rev-parse --short $edit_one`"
+	sed "1s/pick $edit_one /edit $edit_one /" "$todo" > "$todo.new" ||
+		die_abort "failed to update todo list"
+	grep "^edit $edit_one " "$todo.new" >/dev/null ||
+		die_abort "expected to find 'edit $edit_one' line but did not"
+	mv "$todo.new" "$todo" ||
+		die_abort "failed to update todo list"
+else
+	cp "$todo" "$todo".backup
+	git_sequence_editor "$todo" ||
+		die_abort "Could not execute editor"
+fi
 
 has_action "$todo" ||
 	die_abort "Nothing to do"
diff --git a/git-rebase.sh b/git-rebase.sh
index 1cf8dba..98796cc 100755
--- a/git-rebase.sh
+++ b/git-rebase.sh
@@ -31,6 +31,7 @@ verify             allow pre-rebase hook to run
 rerere-autoupdate  allow rerere to update index with resolved conflicts
 root!              rebase all reachable commits up to the root(s)
 autosquash         move commits that begin with squash!/fixup! under -i
+1,edit-one!        generate todo list to edit this commit
 committer-date-is-author-date! passed to 'git am'
 ignore-date!       passed to 'git am'
 whitespace=!       passed to 'git apply'
@@ -249,6 +250,10 @@ do
 	-i)
 		interactive_rebase=explicit
 		;;
+	-1)
+		interactive_rebase=explicit
+		edit_one=t
+		;;
 	-k)
 		keep_empty=yes
 		;;
@@ -450,6 +455,11 @@ then
 		;;
 	*)	upstream_name="$1"
 		shift
+		if test -n "$edit_one"
+		then
+			edit_one="$upstream_name"
+			upstream_name="$upstream_name^"
+		fi
 		;;
 	esac
 	upstream=$(peel_committish "${upstream_name}") ||
-- 
1.9.0.66.g14f785a