rebase -i: generate the script via rebase--helper

The first step of an interactive rebase is to generate the so-called "todo
script", to be stored in the state directory as "git-rebase-todo" and to
be edited by the user.

Originally, we adjusted the output of `git log <options>` using a simple
sed script. Over the course of the years, the code became more
complicated. We now use shell scripting to edit the output of `git log`
conditionally, depending whether to keep "empty" commits (i.e. commits
that do not change any files).

On platforms where shell scripting is not native, this can be a serious
drag. And it opens the door for incompatibilities between platforms when
it comes to shell scripting or to Unix-y commands.

Let's just re-implement the todo script generation in plain C, using the
revision machinery directly.

This is substantially faster, improving the speed relative to the
shell script version of the interactive rebase from 2x to 3x on Windows.

Note that the rearrange_squash() function in git-rebase--interactive
relied on the fact that we set the "format" variable to the config setting
rebase.instructionFormat. Relying on a side effect like this is no good,
hence we explicitly perform that assignment (possibly again) in
rearrange_squash().

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 23 insertions, 21 deletions

diff --git a/git-rebase--interactive.sh b/git-rebase--interactive.sh
index 90b1fbe9cf..05766835de 100644
--- a/git-rebase--interactive.sh
+++ b/git-rebase--interactive.sh
@@ -785,6 +785,7 @@ collapse_todo_ids() {
 # each log message will be re-retrieved in order to normalize the
 # autosquash arrangement
 rearrange_squash () {
+	format=$(git config --get rebase.instructionFormat)
 	# extract fixup!/squash! lines and resolve any referenced sha1's
 	while read -r pick sha1 message
 	do
@@ -1210,26 +1211,27 @@ else
 	revisions=$onto...$orig_head
 	shortrevisions=$shorthead
 fi
-format=$(git config --get rebase.instructionFormat)
-# the 'rev-list .. | sed' requires %m to parse; the instruction requires %H to parse
-git rev-list $merges_option --format="%m%H ${format:-%s}" \
-	--reverse --left-right --topo-order \
-	$revisions ${restrict_revision+^$restrict_revision} | \
-	sed -n "s/^>//p" |
-while read -r sha1 rest
-do
-
-	if test -z "$keep_empty" && is_empty_commit $sha1 && ! is_merge_commit $sha1
-	then
-		comment_out="$comment_char "
-	else
-		comment_out=
-	fi
+if test t != "$preserve_merges"
+then
+	git rebase--helper --make-script ${keep_empty:+--keep-empty} \
+		$revisions ${restrict_revision+^$restrict_revision} >"$todo"
+else
+	format=$(git config --get rebase.instructionFormat)
+	# the 'rev-list .. | sed' requires %m to parse; the instruction requires %H to parse
+	git rev-list $merges_option --format="%m%H ${format:-%s}" \
+		--reverse --left-right --topo-order \
+		$revisions ${restrict_revision+^$restrict_revision} | \
+		sed -n "s/^>//p" |
+	while read -r sha1 rest
+	do
+
+		if test -z "$keep_empty" && is_empty_commit $sha1 && ! is_merge_commit $sha1
+		then
+			comment_out="$comment_char "
+		else
+			comment_out=
+		fi
 
-	if test t != "$preserve_merges"
-	then
-		printf '%s\n' "${comment_out}pick $sha1 $rest" >>"$todo"
-	else
 		if test -z "$rebase_root"
 		then
 			preserve=t
@@ -1248,8 +1250,8 @@ do
 			touch "$rewritten"/$sha1
 			printf '%s\n' "${comment_out}pick $sha1 $rest" >>"$todo"
 		fi
-	fi
-done
+	done
+fi
 
 # Watch for commits that been dropped by --cherry-pick
 if test t = "$preserve_merges"