rebasing-merge: specify all commits explicitly

The earlier attempt to specify additional commits included way too many
commits. So let's start to specify all of the commits explicitly.

While at it, refactor a little and offer a --graph mode that does not
perform the rebasing merge, but shows the commits to be rebased intead.

In the end, it looks like a complete rewrite of the logic, though.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>

share/msysGit/rebasing-merge.sh

@@ -1,7 +1,26 @@
 #!/bin/sh
 
 force=
-case "$1" in -f|--force) shift; force=t;; esac
+graph=
+while test $# -gt 0
+do
+	case "$1" in
+	-f|--force)
+		force=t
+		;;
+	-s|--show|-g|--graph)
+		graph=t
+		;;
+	-*)
+		echo "Unknown option: $1" >&2
+		exit 1
+		;;
+	*)
+		break
+		;;
+	esac
+	shift
+done
 
 TO=${1:-junio/next}
 
@@ -35,58 +54,74 @@ HEAD) ;; # okay
 	;;
 esac
 
-# Find old rebasing merge, if any
+is_ours_merge () {
+	test "$(git rev-parse $1:)" = "$(git rev-parse "$1^:")"
+}
 
-rm -f "$TODO_EXTRA"
+list_merges () {
+	git rev-list --parents "$@" | sed -n 's/ .* .*//p'
+}
 
-MERGE=
-for commit in $(git rev-list --parents $TO.. | sed -n 's/ .* .*//p')
+# Find old rebasing merge, if any
+
+PREVIOUS_REBASING=
+for commit in $(list_merges $TO..)
 do
-	if test "$(git rev-parse $commit:)" = "$(git rev-parse "$commit^:")"
+	if is_ours_merge $commit
 	then
-		MERGE=$commit
+		PREVIOUS_REBASING=$commit
 		break
 	fi
 done
 
-if test -n "$MERGE"
+TO_SHA1=$(git rev-parse --short $TO)
+MESSAGE="Rebasing merge to $TO ($TO_SHA1)"
+RANGE=$TO.. &&
+if test -n "$PREVIOUS_REBASING"
+then
+	MESSAGE="$(printf "%s\n\n%s" "$MESSAGE" \
+		"Previous rebasing merge: $PREVIOUS_REBASING")"
+	RANGE="$RANGE ^$PREVIOUS_REBASING^2"
+	for commit in $(list_merges $RANGE)
+	do
+		test $commit != $PREVIOUS_REBASING &&
+		is_ours_merge $commit &&
+		RANGE="$RANGE ^$commit"
+	done
+fi
+
+if test -n "$graph"
 then
-	ORIG_HEAD=$(git rev-parse HEAD) &&
-	# Find prior merges to $TO
-	EXCLUDE=$(git rev-list --parents $TO..$MERGE^ |
-		sed -n 's/^\([^ ]*\) .* .*/^\1/p') &&
-	# Get commits from previous rebasing merge
-	git rev-list --pretty=oneline --abbrev-commit --abbrev=7 --reverse \
-		--no-merges $TO..$MERGE^ $EXCLUDE |
-	sed 's/^/pick /' > "$TODO_EXTRA" &&
-	TMP_EDITOR="$(git rev-parse --git-dir)/rebasing-editor.sh" &&
-	cat > "$TMP_EDITOR" << EOF &&
+	git log --graph --oneline --boundary $RANGE
+	exit
+fi
+
+ORIG_HEAD=$(git rev-parse HEAD)
+# Get commits to rebase
+git rev-list --format='pick %h %s (%an)' --reverse --no-merges $RANGE |
+grep -v '^commit ' > "$TODO_EXTRA" &&
+TMP_EDITOR="$(git rev-parse --git-dir)/rebasing-editor.sh" &&
+cat > "$TMP_EDITOR" << EOF &&
 #!/bin/sh
 case "\$1" in
 */git-rebase-todo)
-	cat "\$1" >> "$TODO_EXTRA" &&
+	sed -e '/^[^#]/d' < "\$1" >> "$TODO_EXTRA" &&
 	mv "$TODO_EXTRA" "\$1"
 esac &&
 exec "$(git var GIT_EDITOR)" "\$@"
 EOF
-	TO_SHA1=$(git rev-parse --short $TO) &&
-	chmod a+x "$TMP_EDITOR" &&
-	if GIT_EDITOR="$TMP_EDITOR" git rebase -i --onto $TO $MERGE
-	then
-		git merge -s ours -m "Rebasing merge to $TO ($TO_SHA1)" \
-			$ORIG_HEAD
-	else
-		FINISH="$(git rev-parse --git-dir)/finish-rebasing-merge.sh"
-		cat > "$FINISH" << EOF
-git merge -s ours -m "Rebasing merge to $TO ($TO_SHA1)" $ORIG_HEAD
+chmod a+x "$TMP_EDITOR" &&
+if GIT_EDITOR="$TMP_EDITOR" git rebase --autosquash -i --onto $TO HEAD^
+then
+	git merge -s ours -m "$MESSAGE" $ORIG_HEAD
+else
+	FINISH="$(git rev-parse --git-dir)/finish-rebasing-merge.sh"
+	cat > "$FINISH" << EOF
+git merge -s ours -m '$MESSAGE' $ORIG_HEAD
 EOF
-		chmod a+x "$FINISH"
-		cat << EOF
+	chmod a+x "$FINISH"
+	cat << EOF
 
 After the rebase, call '$FINISH' manually
 EOF
-	fi
-
-else
-	git rebase --autosquash -i $TO
 fi