git-rebase--interactive.sh: add config option for custom instruction format

A config option 'rebase.instructionFormat' can override the
default 'oneline' format of the rebase instruction list.

Since the list is parsed using the left, right or boundary mark plus
the sha1, they are prepended to the instruction format.

Signed-off-by: Michael Rappazzo <rappazzo@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/config.txt

@@ -2160,6 +2160,11 @@ rebase.autoStash::
 	successful rebase might result in non-trivial conflicts.
 	Defaults to false.
 
+rebase.instructionFormat
+	A format string, as specified in linkgit:git-log[1], to be used for
+	the instruction list during an interactive rebase.  The format will automatically
+	have the long commit hash prepended to the format.
+
 receive.advertiseAtomic::
 	By default, git-receive-pack will advertise the atomic push
 	capability to its clients. If you don't want to this capability

Documentation/git-rebase.txt

@@ -213,6 +213,9 @@ rebase.autoSquash::
 rebase.autoStash::
 	If set to true enable '--autostash' option by default.
 
+rebase.instructionFormat::
+	Custom commit list format to use during an '--interactive' rebase.
+
 OPTIONS
 -------
 --onto <newbase>::
@@ -359,6 +362,10 @@ default is `--no-fork-point`, otherwise the default is `--fork-point`.
 	Make a list of the commits which are about to be rebased.  Let the
 	user edit that list before rebasing.  This mode can also be used to
 	split commits (see SPLITTING COMMITS below).
++
+The commit list format can be changed by setting the configuration option
+rebase.instructionFormat.  A customized instruction format will automatically
+have the long commit hash prepended to the format.
 
 -p::
 --preserve-merges::

git-rebase--interactive.sh

@@ -740,10 +740,15 @@ collapse_todo_ids() {
 # "pick sha1 fixup!/squash! msg" appears in it so that the latter
 # comes immediately after the former, and change "pick" to
 # "fixup"/"squash".
+#
+# Note that if the config has specified a custom instruction format
+# each log message will be re-retrieved in order to normalize the
+# autosquash arrangement
 rearrange_squash () {
 	# extract fixup!/squash! lines and resolve any referenced sha1's
 	while read -r pick sha1 message
 	do
+		test -z "${format}" || message=$(git log -n 1 --format="%s" ${sha1})
 		case "$message" in
 		"squash! "*|"fixup! "*)
 			action="${message%%!*}"
@@ -785,6 +790,7 @@ rearrange_squash () {
 		*" $sha1 "*) continue ;;
 		esac
 		printf '%s\n' "$pick $sha1 $message"
+		test -z "${format}" || message=$(git log -n 1 --format="%s" ${sha1})
 		used="$used$sha1 "
 		while read -r squash action msg_prefix msg_content
 		do
@@ -802,8 +808,13 @@ rearrange_squash () {
 				case "$message" in "$msg_content"*) emit=1;; esac ;;
 			esac
 			if test $emit = 1; then
-				real_prefix=$(echo "$msg_prefix" | sed "s/,/! /g")
-				printf '%s\n' "$action $squash ${real_prefix}$msg_content"
+				if test -n "${format}"
+				then
+					msg_content=$(git log -n 1 --format="${format}" ${squash})
+				else
+					msg_content="$(echo "$msg_prefix" | sed "s/,/! /g")$msg_content"
+				fi
+				printf '%s\n' "$action $squash $msg_content"
 				used="$used$squash "
 			fi
 		done <"$1.sq"
@@ -977,7 +988,10 @@ else
 	revisions=$onto...$orig_head
 	shortrevisions=$shorthead
 fi
-git rev-list $merges_option --pretty=oneline --reverse --left-right --topo-order \
+format=$(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

t/t3415-rebase-autosquash.sh

@@ -250,4 +250,25 @@ test_expect_success 'squash! fixup!' '
 	test_auto_fixup_fixup squash fixup
 '
 
+test_expect_success 'autosquash with custom inst format' '
+	git reset --hard base &&
+	git config --add rebase.instructionFormat "[%an @ %ar] %s"  &&
+	echo 2 >file1 &&
+	git add -u &&
+	test_tick &&
+	git commit -m "squash! $(git rev-parse --short HEAD^)" &&
+	echo 1 >file1 &&
+	git add -u &&
+	test_tick &&
+	git commit -m "squash! $(git log -n 1 --format=%s HEAD~2)" &&
+	git tag final-squash-instFmt &&
+	test_tick &&
+	git rebase --autosquash -i HEAD~4 &&
+	git log --oneline >actual &&
+	test_line_count = 3 actual &&
+	git diff --exit-code final-squash-instFmt &&
+	test 1 = "$(git cat-file blob HEAD^:file1)" &&
+	test 2 = $(git cat-file commit HEAD^ | grep squash | wc -l)
+'
+
 test_done