Re: [GSoC][PATCH v5 11/20] rebase -i: rewrite complete_action() in C

[Phillip Wood <phillip.wood@talktalk.net>]

Hi Alban

Its nice to see things coming together so that the rebase happens in the 
same process as the some of the todo file preparation. I've ended up 
making quite a few comments on the new implementation, but they're all 
little things, the basic idea looks sound to me.

On 31/07/18 18:59, Alban Gruin wrote:
> This rewrites complete_action() from shell to C.
> 
> A new mode is added to rebase--helper (`--complete-action`), as well as
> a new flag (`--autosquash`).
> 
> Finally, complete_action() is stripped from git-rebase--interactive.sh.
> 
> The original complete_action() would return the code 2 when the todo
> list contained no actions.  This was a special case for rebase -i and
> -p; git-rebase.sh would then apply the autostash, delete the state
> directory, and die with the message "Nothing to do".  This cleanup is
> rewritten in C instead of returning 2.  As rebase -i no longer returns
> 2, the comment describing this behaviour in git-rebase.sh is updated to
> reflect this change.
> 
> The first check might seem useless as we write "noop" to the todo list
> if it is empty.  Actually, the todo list might contain commented
> commands (ie. empty commits).  In this case, complete_action() won’t
> write "noop", and will abort without starting the editor.
> 
> Signed-off-by: Alban Gruin <alban.gruin@gmail.com>
> ---
> No changes since v4.
> 
>   builtin/rebase--helper.c   | 12 ++++-
>   git-rebase--interactive.sh | 53 ++------------------
>   git-rebase.sh              |  2 +-
>   sequencer.c                | 99 ++++++++++++++++++++++++++++++++++++++
>   sequencer.h                |  4 ++
>   5 files changed, 118 insertions(+), 52 deletions(-)
> 
> diff --git a/builtin/rebase--helper.c b/builtin/rebase--helper.c
> index bed3dd2b95..d7fa5a5062 100644
> --- a/builtin/rebase--helper.c
> +++ b/builtin/rebase--helper.c
> @@ -13,13 +13,13 @@ 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, autosquash = 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, APPEND_TODO_HELP, EDIT_TODO, PREPARE_BRANCH,
> -		CHECKOUT_ONTO
> +		CHECKOUT_ONTO, COMPLETE_ACTION
>   	} command = 0;
>   	struct option options[] = {
>   		OPT_BOOL(0, "ff", &opts.allow_ff, N_("allow fast-forward")),
> @@ -29,6 +29,8 @@ 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, "autosquash", &autosquash,
> +			 N_("move commits thas begin with squash!/fixup!")),

s/thas/that/

>   		OPT__VERBOSE(&opts.verbose, N_("be verbose")),
>   		OPT_CMDMODE(0, "continue", &command, N_("continue rebase"),
>   				CONTINUE),
> @@ -57,6 +59,8 @@ int cmd_rebase__helper(int argc, const char **argv, const char *prefix)
>   			    N_("prepare the branch to be rebased"), PREPARE_BRANCH),
>   		OPT_CMDMODE(0, "checkout-onto", &command,
>   			    N_("checkout a commit"), CHECKOUT_ONTO),
> +		OPT_CMDMODE(0, "complete-action", &command,
> +			    N_("complete the action"), COMPLETE_ACTION),
>   		OPT_END()
>   	};
>   
> @@ -110,5 +114,9 @@ int cmd_rebase__helper(int argc, const char **argv, const char *prefix)
>   		return !!prepare_branch_to_be_rebased(&opts, argv[1]);
>   	if (command == CHECKOUT_ONTO && argc == 4)
>   		return !!checkout_onto(&opts, argv[1], argv[2], argv[3]);
> +	if (command == COMPLETE_ACTION && argc == 6)
> +		return !!complete_action(&opts, flags, argv[1], argv[2], argv[3],
> +					 argv[4], argv[5], autosquash);
> +
>   	usage_with_options(builtin_rebase_helper_usage, options);
>   }
> diff --git a/git-rebase--interactive.sh b/git-rebase--interactive.sh
> index b68f108f28..59dc4888a6 100644
> --- a/git-rebase--interactive.sh
> +++ b/git-rebase--interactive.sh
> @@ -127,54 +127,6 @@ init_revisions_and_shortrevisions () {
>   	fi
>   }
>   
> -complete_action() {
> -	test -s "$todo" || echo noop >> "$todo"
> -	test -z "$autosquash" || git rebase--helper --rearrange-squash || exit
> -	test -n "$cmd" && git rebase--helper --add-exec-commands "$cmd"
> -
> -	todocount=$(git stripspace --strip-comments <"$todo" | wc -l)
> -	todocount=${todocount##* }
> -
> -cat >>"$todo" <<EOF
> -
> -$comment_char $(eval_ngettext \
> -	"Rebase \$shortrevisions onto \$shortonto (\$todocount command)" \
> -	"Rebase \$shortrevisions onto \$shortonto (\$todocount commands)" \
> -	"$todocount")
> -EOF
> -	git rebase--helper --append-todo-help ${keep_empty:+--keep-empty}
> -
> -	has_action "$todo" ||
> -		return 2
> -
> -	cp "$todo" "$todo".backup
> -	collapse_todo_ids
> -	git_sequence_editor "$todo" ||
> -		die_abort "$(gettext "Could not execute editor")"
> -
> -	has_action "$todo" ||
> -		return 2
> -
> -	git rebase--helper --check-todo-list || {
> -		ret=$?
> -		git rebase--helper --checkout-onto "$onto_name" "$onto" \
> -		    "$orig_head" ${verbose:+--verbose}
> -		exit $ret
> -	}
> -
> -	expand_todo_ids
> -
> -	test -n "$force_rebase" ||
> -	onto="$(git rebase--helper --skip-unnecessary-picks)" ||
> -	die "Could not skip unnecessary pick commands"
> -
> -	git rebase--helper --checkout-onto "$onto_name" "$onto" "$orig_head" \
> -	    ${verbose:+--verbose}
> -	require_clean_work_tree "rebase"
> -	exec git rebase--helper ${force_rebase:+--no-ff} $allow_empty_message \
> -	     --continue
> -}
> -
>   git_rebase__interactive () {
>   	initiate_action "$action"
>   	ret=$?
> @@ -193,5 +145,8 @@ git_rebase__interactive () {
>   		$revisions ${restrict_revision+^$restrict_revision} >"$todo" ||
>   	die "$(gettext "Could not generate todo list")"
>   
> -	complete_action
> +	exec git rebase--helper --complete-action "$shortrevisions" "$onto_name" \
> +		"$shortonto" "$orig_head" "$cmd" $allow_empty_message \
> +		${autosquash:+--autosquash} ${keep_empty:+--keep-empty} \
> +		${verbose:+--verbose} ${force_rebase:+--no-ff}
>   }
> diff --git a/git-rebase.sh b/git-rebase.sh
> index 7973447645..51a6db7daa 100755
> --- a/git-rebase.sh
> +++ b/git-rebase.sh
> @@ -219,7 +219,7 @@ run_specific_rebase () {
>   	if test $ret -eq 0
>   	then
>   		finish_rebase
> -	elif test $ret -eq 2 # special exit status for rebase -i
> +	elif test $ret -eq 2 # special exit status for rebase -p
>   	then
>   		apply_autostash &&
>   		rm -rf "$state_dir" &&
> diff --git a/sequencer.c b/sequencer.c
> index a2e04b9eca..8102e24b19 100644
> --- a/sequencer.c
> +++ b/sequencer.c
> @@ -30,6 +30,7 @@
>   #include "oidset.h"
>   #include "commit-slab.h"
>   #include "alias.h"
> +#include "rebase-interactive.h"
>   
>   #define GIT_REFLOG_ACTION "GIT_REFLOG_ACTION"
>   
> @@ -53,6 +54,9 @@ static GIT_PATH_FUNC(rebase_path, "rebase-merge")
>    * file and written to the tail of 'done'.
>    */
>   GIT_PATH_FUNC(rebase_path_todo, "rebase-merge/git-rebase-todo")
> +static GIT_PATH_FUNC(rebase_path_todo_backup,
> +		     "rebase-merge/git-rebase-todo.backup")
> +
>   /*
>    * The rebase command lines that have already been processed. A line
>    * is moved here when it is first handled, before any associated user
> @@ -4499,6 +4503,101 @@ int skip_unnecessary_picks(struct object_id *output_oid)
>   	return 0;
>   }
>   
> +int complete_action(struct replay_opts *opts, unsigned flags,
> +		    const char *shortrevisions, const char *onto_name,
> +		    const char *onto, const char *orig_head, const char *cmd,
> +		    unsigned autosquash)
> +{
> +	const char *shortonto, *todo_file = rebase_path_todo();
> +	struct todo_list todo_list = TODO_LIST_INIT;
> +	struct strbuf *buf = &(todo_list.buf);
> +	struct object_id oid;
> +	struct stat st;
> +
> +	get_oid(onto, &oid);

Is onto guaranteed to exist? If not the return value of get_oid() needs 
to be checked. Otherwise a comment or an assertion might be useful here.

> +	shortonto = find_unique_abbrev(&oid, DEFAULT_ABBREV);
> +
> +	if (!lstat(todo_file, &st) && st.st_size == 0 &&
> +	    write_message("noop\n", 5, todo_file, 0))
> +		return error_errno(_("could not write '%s'"), todo_file);
> +
> +	if (autosquash && rearrange_squash())
> +		return 1;

git functions normally return -1 for an error as the 'return error(...)' 
does above, is there a reason for a different return value here?

> +
> +	if (cmd && *cmd)
> +		sequencer_add_exec_commands(cmd); > +
> +	if (strbuf_read_file(buf, todo_file, 0) < 0)
> +		return error_errno(_("could not read '%s'."), todo_file);
> +
> +	if (parse_insn_buffer(buf->buf, &todo_list)) {

I was worried when I saw this because buf is an alias of todo_list.buf 
and I thought passing the same buffer in twice would end badly. However 
parse_insn_buffer() has a confusing signature, it expects the caller to 
have filled todo_list.buf with the buffer to be parsed and to pass a 
pointer to the same buffer. I think this should be cleaned up at some 
point but it is outside the scope of this series.

> +		todo_list_release(&todo_list);
> +		return error(_("unusable todo list: '%s'"), todo_file);
> +	}
> +
> +	if (count_commands(&todo_list) == 0) {
> +		apply_autostash(opts);
> +		sequencer_remove_state(opts);
> +		todo_list_release(&todo_list);
> +
> +		fputs("Nothing to do\n", stderr);

The capital 'N' is a faithful copy of the current message in rebase.sh. 
However it might be worth changing it to 'n' to match the normal style 
of git error messages starting with a lowercase letter.

> +		return 1;

It might be better to do 'return error(...)' instead

> +	}
> +
> +	strbuf_addch(buf, '\n');
> +	strbuf_commented_addf(buf, Q_("Rebase %s onto %s (%d command)",
> +				      "Rebase %s onto %s (%d commands)",
> +				      count_commands(&todo_list)),
> +			      shortrevisions, shortonto, count_commands(&todo_list));
> +	append_todo_help(0, flags & TODO_LIST_KEEP_EMPTY, buf);
> +
> +	if (write_message(buf->buf, buf->len, todo_file, 0)) {
> +		todo_list_release(&todo_list);
> +		return error_errno(_("could not write '%s'"), todo_file);
> +	}
> +
> +	copy_file(rebase_path_todo_backup(), todo_file, 0666);
> +	transform_todos(flags | TODO_LIST_SHORTEN_IDS);

Both of the above lines can fail, so the return values need checking I 
think.

> +
> +	strbuf_reset(buf);
> +
> +	if (launch_sequence_editor(todo_file, buf, NULL)) {
> +		apply_autostash(opts);
> +		sequencer_remove_state(opts);
> +		todo_list_release(&todo_list);
> +
> +		return error(_("could not execute editor"));

I think  launch_sequence_editor() will have printed an error message 
already, so this is unnecessary.

> +	}
> +
> +	strbuf_stripspace(buf, 1);
> +	if (buf->len == 0) {
> +		apply_autostash(opts);
> +		sequencer_remove_state(opts);
> +		todo_list_release(&todo_list);
> +
> +		fputs("Nothing to do\n", stderr);
> +		return 1;

See my comments above about 'N' and using 'return error(...)'

> +	}
> +
> +	todo_list_release(&todo_list);
> +
> +	if (check_todo_list()) {
> +		checkout_onto(opts, onto_name, onto, orig_head);
> +		return 1;

s/1/-1/?

> +	}
> +
> +	transform_todos(flags & ~(TODO_LIST_SHORTEN_IDS));

I think the return value of transform_todos() needs to be checked

> +	if (opts->allow_ff && skip_unnecessary_picks(&oid))
> +		return error(_("could not skip unnecessary pick commands"));
> +
> +	checkout_onto(opts, onto_name, oid_to_hex(&oid), orig_head);
> +	if (require_clean_work_tree("rebase", "", 1, 1))
> +		return 1;

s/1/-1/?

Best Wishes

Phillip

> +
> +	return sequencer_continue(opts);
> +}
> +
>   struct subject2item_entry {
>   	struct hashmap_entry entry;
>   	int i;
> diff --git a/sequencer.h b/sequencer.h
> index f11dabfd65..3ab3791c8a 100644
> --- a/sequencer.h
> +++ b/sequencer.h
> @@ -89,6 +89,10 @@ int transform_todos(unsigned flags);
>   enum missing_commit_check_level get_missing_commit_check_level(void);
>   int check_todo_list(void);
>   int skip_unnecessary_picks(struct object_id *output_oid);
> +int complete_action(struct replay_opts *opts, unsigned flags,
> +		    const char *shortrevisions, const char *onto_name,
> +		    const char *onto, const char *orig_head, const char *cmd,
> +		    unsigned autosquash);
>   int rearrange_squash(void);
>   
>   extern const char sign_off_header[];
>