rebase -i: rewrite append_todo_help() in C

This rewrites append_todo_help() from shell to C. It also incorporates
some parts of initiate_action() and complete_action() that also write
help texts to the todo file.

This also introduces the source file rebase-interactive.c. This file
will contain functions necessary for interactive rebase that are too
specific for the sequencer, and is part of libgit.a.

Two flags are added to rebase--helper.c: one to call
append_todo_help() (`--append-todo-help`), and another one to tell
append_todo_help() to write the help text suited for the edit-todo
mode (`--write-edit-todo`).

Finally, append_todo_help() is removed from git-rebase--interactive.sh
to use `rebase--helper --append-todo-help` instead.

Signed-off-by: Alban Gruin <alban.gruin@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

5 files changed, 86 insertions, 52 deletions

diff --git a/Makefile b/Makefile
index 08e5c54549..909a687857 100644
--- a/Makefile
+++ b/Makefile
@@ -922,6 +922,7 @@ LIB_OBJS += protocol.o
 LIB_OBJS += quote.o
 LIB_OBJS += reachable.o
 LIB_OBJS += read-cache.o
+LIB_OBJS += rebase-interactive.o
 LIB_OBJS += reflog-walk.o
 LIB_OBJS += refs.o
 LIB_OBJS += refs/files-backend.o
diff --git a/builtin/rebase--helper.c b/builtin/rebase--helper.c
index f7c2a5fdc8..05e73e71d4 100644
--- a/builtin/rebase--helper.c
+++ b/builtin/rebase--helper.c
@@ -3,6 +3,7 @@
 #include "config.h"
 #include "parse-options.h"
 #include "sequencer.h"
+#include "rebase-interactive.h"
 
 static const char * const builtin_rebase_helper_usage[] = {
 	N_("git rebase--helper [<options>]"),
@@ -12,12 +13,12 @@ static const char * const builtin_rebase_helper_usage[] = {
 int cmd_rebase__helper(int argc, const char **argv, const char *prefix)
 {
 	struct replay_opts opts = REPLAY_OPTS_INIT;
-	unsigned flags = 0, keep_empty = 0, rebase_merges = 0;
+	unsigned flags = 0, keep_empty = 0, rebase_merges = 0, write_edit_todo = 0;
 	int abbreviate_commands = 0, rebase_cousins = -1;
 	enum {
 		CONTINUE = 1, ABORT, MAKE_SCRIPT, SHORTEN_OIDS, EXPAND_OIDS,
 		CHECK_TODO_LIST, SKIP_UNNECESSARY_PICKS, REARRANGE_SQUASH,
-		ADD_EXEC
+		ADD_EXEC, APPEND_TODO_HELP
 	} command = 0;
 	struct option options[] = {
 		OPT_BOOL(0, "ff", &opts.allow_ff, N_("allow fast-forward")),
@@ -27,6 +28,8 @@ int cmd_rebase__helper(int argc, const char **argv, const char *prefix)
 		OPT_BOOL(0, "rebase-merges", &rebase_merges, N_("rebase merge commits")),
 		OPT_BOOL(0, "rebase-cousins", &rebase_cousins,
 			 N_("keep original branch points of cousins")),
+		OPT_BOOL(0, "write-edit-todo", &write_edit_todo,
+			 N_("append the edit-todo message to the todo-list")),
 		OPT_CMDMODE(0, "continue", &command, N_("continue rebase"),
 				CONTINUE),
 		OPT_CMDMODE(0, "abort", &command, N_("abort rebase"),
@@ -45,6 +48,8 @@ int cmd_rebase__helper(int argc, const char **argv, const char *prefix)
 			N_("rearrange fixup/squash lines"), REARRANGE_SQUASH),
 		OPT_CMDMODE(0, "add-exec-commands", &command,
 			N_("insert exec commands in todo list"), ADD_EXEC),
+		OPT_CMDMODE(0, "append-todo-help", &command,
+			    N_("insert the help in the todo list"), APPEND_TODO_HELP),
 		OPT_END()
 	};
 
@@ -84,5 +89,7 @@ int cmd_rebase__helper(int argc, const char **argv, const char *prefix)
 		return !!rearrange_squash();
 	if (command == ADD_EXEC && argc == 2)
 		return !!sequencer_add_exec_commands(argv[1]);
+	if (command == APPEND_TODO_HELP && argc == 1)
+		return !!append_todo_help(write_edit_todo, keep_empty);
 	usage_with_options(builtin_rebase_helper_usage, options);
 }
diff --git a/git-rebase--interactive.sh b/git-rebase--interactive.sh
index 299ded2137..94c23a7af2 100644
--- a/git-rebase--interactive.sh
+++ b/git-rebase--interactive.sh
@@ -39,38 +39,6 @@ comment_for_reflog () {
 	esac
 }
 
-append_todo_help () {
-	gettext "
-Commands:
-p, pick <commit> = use commit
-r, reword <commit> = use commit, but edit the commit message
-e, edit <commit> = use commit, but stop for amending
-s, squash <commit> = use commit, but meld into previous commit
-f, fixup <commit> = like \"squash\", but discard this commit's log message
-x, exec <command> = run command (the rest of the line) using shell
-d, drop <commit> = remove commit
-l, label <label> = label current HEAD with a name
-t, reset <label> = reset HEAD to a label
-m, merge [-C <commit> | -c <commit>] <label> [# <oneline>]
-.       create a merge commit using the original merge commit's
-.       message (or the oneline, if no original merge commit was
-.       specified). Use -c <commit> to reword the commit message.
-
-These lines can be re-ordered; they are executed from top to bottom.
-" | git stripspace --comment-lines >>"$todo"
-
-	if test $(get_missing_commit_check_level) = error
-	then
-		gettext "
-Do not remove any line. Use 'drop' explicitly to remove a commit.
-" | git stripspace --comment-lines >>"$todo"
-	else
-		gettext "
-If you remove a line here THAT COMMIT WILL BE LOST.
-" | git stripspace --comment-lines >>"$todo"
-	fi
-}
-
 die_abort () {
 	apply_autostash
 	rm -rf "$state_dir"
@@ -143,13 +111,7 @@ initiate_action () {
 		git stripspace --strip-comments <"$todo" >"$todo".new
 		mv -f "$todo".new "$todo"
 		collapse_todo_ids
-		append_todo_help
-		gettext "
-You are editing the todo file of an ongoing interactive rebase.
-To continue rebase after editing, run:
-    git rebase --continue
-
-" | git stripspace --comment-lines >>"$todo"
+		git rebase--helper --append-todo-help --write-edit-todo
 
 		git_sequence_editor "$todo" ||
 			die "$(gettext "Could not execute editor")"
@@ -220,17 +182,7 @@ $comment_char $(eval_ngettext \
 	"Rebase \$shortrevisions onto \$shortonto (\$todocount commands)" \
 	"$todocount")
 EOF
-	append_todo_help
-	gettext "
-	However, if you remove everything, the rebase will be aborted.
-
-	" | git stripspace --comment-lines >>"$todo"
-
-	if test -z "$keep_empty"
-	then
-		printf '%s\n' "$comment_char $(gettext "Note that empty commits are commented out")" >>"$todo"
-	fi
-
+	git rebase--helper --append-todo-help ${keep_empty:+--keep-empty}
 
 	has_action "$todo" ||
 		return 2
diff --git a/rebase-interactive.c b/rebase-interactive.c
new file mode 100644
index 0000000000..d7996bc8d9
--- /dev/null
+++ b/rebase-interactive.c
@@ -0,0 +1,68 @@
+#include "cache.h"
+#include "commit.h"
+#include "rebase-interactive.h"
+#include "sequencer.h"
+#include "strbuf.h"
+
+int append_todo_help(unsigned edit_todo, unsigned keep_empty)
+{
+	struct strbuf buf = STRBUF_INIT;
+	FILE *todo;
+	int ret;
+	const char *msg = _("\nCommands:\n"
+"p, pick <commit> = use commit\n"
+"r, reword <commit> = use commit, but edit the commit message\n"
+"e, edit <commit> = use commit, but stop for amending\n"
+"s, squash <commit> = use commit, but meld into previous commit\n"
+"f, fixup <commit> = like \"squash\", but discard this commit's log message\n"
+"x, exec <command> = run command (the rest of the line) using shell\n"
+"d, drop <commit> = remove commit\n"
+"l, label <label> = label current HEAD with a name\n"
+"t, reset <label> = reset HEAD to a label\n"
+"m, merge [-C <commit> | -c <commit>] <label> [# <oneline>]\n"
+".       create a merge commit using the original merge commit's\n"
+".       message (or the oneline, if no original merge commit was\n"
+".       specified). Use -c <commit> to reword the commit message.\n"
+"\n"
+"These lines can be re-ordered; they are executed from top to bottom.\n");
+
+	todo = fopen_or_warn(rebase_path_todo(), "a");
+	if (!todo)
+		return 1;
+
+	strbuf_add_commented_lines(&buf, msg, strlen(msg));
+
+	if (get_missing_commit_check_level() == MISSING_COMMIT_CHECK_ERROR)
+		msg = _("\nDo not remove any line. Use 'drop' "
+			 "explicitly to remove a commit.\n");
+	else
+		msg = _("\nIf you remove a line here "
+			 "THAT COMMIT WILL BE LOST.\n");
+
+	strbuf_add_commented_lines(&buf, msg, strlen(msg));
+
+	if (edit_todo)
+		msg = _("\nYou are editing the todo file "
+			"of an ongoing interactive rebase.\n"
+			"To continue rebase after editing, run:\n"
+			"    git rebase --continue\n\n");
+	else
+		msg = _("\nHowever, if you remove everything, "
+			"the rebase will be aborted.\n\n");
+
+	strbuf_add_commented_lines(&buf, msg, strlen(msg));
+
+	if (!keep_empty) {
+		msg = _("Note that empty commits are commented out");
+		strbuf_add_commented_lines(&buf, msg, strlen(msg));
+	}
+
+	ret = fputs(buf.buf, todo);
+	if (ret < 0)
+		error_errno(_("could not append help text to '%s'"), rebase_path_todo());
+
+	fclose(todo);
+	strbuf_release(&buf);
+
+	return ret;
+}
diff --git a/rebase-interactive.h b/rebase-interactive.h
new file mode 100644
index 0000000000..47372624e0
--- /dev/null
+++ b/rebase-interactive.h
@@ -0,0 +1,6 @@
+#ifndef REBASE_INTERACTIVE_H
+#define REBASE_INTERACTIVE_H
+
+int append_todo_help(unsigned edit_todo, unsigned keep_empty);
+
+#endif