Subject: Re: [PATCH v4 2/2] rebase-interactive: warn if commit is dropped with `rebase --edit-todo'

From: Phillip Wood <[email-masked]>
Date: Sun, 19 Jan 2020 16:28:49 +0000

Hi Alban

On 11/01/2020 17:39, Alban Gruin wrote:
> When set to "warn" or "error", `rebase.missingCommitsCheck' would make
> `rebase -i' warn if the user removed commits from the todo list to
> prevent mistakes.  Unfortunately, `rebase --edit-todo' and `rebase
> --continue' don't take it into account.
> 
> This adds the ability for `rebase --edit-todo' and `rebase --continue'
> to check if commits were dropped by the user.  As both edit_todo_list()
> and complete_action() parse the todo list and check for dropped commits,
> the code doing so in the latter is removed to reduce duplication.
> `edit_todo_list_advice' is removed from sequencer.c as it is no longer
> used there.
> 
> This changes when a backup of the todo list is made.  Until now, it
> was saved only once, before the initial edit.  Now, it is also made if
> after the user edited the list, if it has no errors or if no commits
> were dropped and `rebase.missingCommitsCheck' is set.  Thus, the
> backup should be error-free.  Without this, sequencer_continue()
> (`rebase --continue') could only compare the current todo list against
> the original, unedited list.  Before this change, this file was only
> used by edit_todo_list() and `rebase -p' to create the backup before
> the initial edit, and check_todo_list_from_file(), only used by
> `rebase -p' to check for dropped commits after its own initial edit.
> 
> If the edited list has an error, a file, `dropped', is created to
> report the issue.  Otherwise, it is deleted.  Usually, the edited list
> is compared against the list before editing, but if this file exists,
> it will be compared to the backup.  Also, if the file exists,
> sequencer_continue() checks the list for dropped commits.  If the
> check was performed every time, it would fail when resuming a rebase
> after resolving a conflict, as the backup will contain commits that
> were picked, but they will not be in the new list.  It's safe to
> ignore this check if `dropped' does not exist, because that means that
> no errors were found at the last edition, so any missing commits here
> have already been picked.
> 
> Four tests are added to t3404.  The tests for
> `rebase.missingCommitsCheck = warn' and `rebase.missingCommitsCheck =
> error' have a similar structure.  First, we start a rebase with an
> incorrect command on the first line.  Then, we edit the todo list,
> removing the first and the last lines.  This demonstrates that
> `--edit-todo' notices dropped commits, but not when the command is
> incorrect.  Then, we restore the original todo list, and edit it to
> remove the last line.  This demonstrates that if we add a commit after
> the initial edit, then remove it, `--edit-todo' will notice that it
> has been dropped.  Then, the actual rebase takes place.  In the third
> test, it is also checked that `--continue' will refuse to resume the
> rebase if commits were dropped.  The fourth test checks that no errors
> are raised when resuming a rebase after resolving a conflict.
> 
> Signed-off-by: Alban Gruin <[email-masked]>
> ---
> 
> Notes:
>      I don't think the way I create `expect.3' files in "rebase --edit-todo
>      respects rebase.missingCommitsCheck = warning" & "... = error" is the
>      best practice.  Perhaps I should create a new file from scratch instead
>      of calling `head' and `tail' successively?
> 
>   rebase-interactive.c          |  58 ++++++++++++++----
>   rebase-interactive.h          |   3 +
>   sequencer.c                   |  22 +++----
>   sequencer.h                   |   1 +
>   t/t3404-rebase-interactive.sh | 109 ++++++++++++++++++++++++++++++++++
>   5 files changed, 171 insertions(+), 22 deletions(-)
> 
> diff --git a/rebase-interactive.c b/rebase-interactive.c
> index ad5dd49c31..36b08a55ef 100644
> --- a/rebase-interactive.c
> +++ b/rebase-interactive.c
> @@ -5,6 +5,7 @@
>   #include "strbuf.h"
>   #include "commit-slab.h"
>   #include "config.h"
> +#include "dir.h"
>   
>   static const char edit_todo_list_advice[] =
>   N_("You can fix this with 'git rebase --edit-todo' "
> @@ -97,22 +98,25 @@ int edit_todo_list(struct repository *r, struct todo_list *todo_list,
>   		   struct todo_list *new_todo, const char *shortrevisions,
>   		   const char *shortonto, unsigned flags)
>   {
> -	const char *todo_file = rebase_path_todo();
> +	const char *todo_file = rebase_path_todo(),
> +		*todo_backup = rebase_path_todo_backup();
>   	unsigned initial = shortrevisions && shortonto;
> +	int incorrect = 1;
>   
>   	/* If the user is editing the todo list, we first try to parse
>   	 * it.  If there is an error, we do not return, because the user
>   	 * might want to fix it in the first place. */
>   	if (!initial)
> -		todo_list_parse_insn_buffer(r, todo_list->buf.buf, todo_list);
> +		incorrect = todo_list_parse_insn_buffer(r, todo_list->buf.buf, todo_list);
> +
> +	incorrect |= file_exists(rebase_path_dropped());
>   
>   	if (todo_list_write_to_file(r, todo_list, todo_file, shortrevisions, shortonto,
>   				    -1, flags | TODO_LIST_SHORTEN_IDS | TODO_LIST_APPEND_TODO_HELP))
>   		return error_errno(_("could not write '%s'"), todo_file);
>   
> -	if (initial && copy_file(rebase_path_todo_backup(), todo_file, 0666))
> -		return error(_("could not copy '%s' to '%s'."), todo_file,
> -			     rebase_path_todo_backup());
> +	if (initial && copy_file(todo_backup, todo_file, 0666))
> +		return error(_("could not copy '%s' to '%s'."), todo_file, todo_backup);
>   
>   	if (launch_sequence_editor(todo_file, &new_todo->buf, NULL))
>   		return -2;
> @@ -121,10 +125,26 @@ int edit_todo_list(struct repository *r, struct todo_list *todo_list,
>   	if (initial && new_todo->buf.len == 0)
>   		return -3;
>   
> -	/* For the initial edit, the todo list gets parsed in
> -	 * complete_action(). */
> -	if (!initial)
> -		return todo_list_parse_insn_buffer(r, new_todo->buf.buf, new_todo);
> +	if (todo_list_parse_insn_buffer(r, new_todo->buf.buf, new_todo)) {
> +		fprintf(stderr, _(edit_todo_list_advice));
> +		return -4;
> +	}
> +
> +	if (incorrect) {
> +		if (todo_list_check_against_backup(r, new_todo)) {
> +			write_file(rebase_path_dropped(), "");
> +			return -4;
> +		}
> +
> +		if (incorrect > 0)
> +			unlink(rebase_path_dropped());
> +	} else if (todo_list_check(todo_list, new_todo)) {
> +		write_file(rebase_path_dropped(), "");

We also need to create a backup from todo_list otherwise we'll be using
a stale backup file for the in the clause above when the user edits the
todo list to fix it. This test fails

test_expect_success 'rebase.missingCommitsCheck = error when editing for a second time' '
	test_config rebase.missingCommitsCheck error &&
	(
		set_fake_editor &&
		FAKE_LINES="1 break 2 3" git rebase -i A D &&
		cp .git/rebase-merge/git-rebase-todo todo &&
		test_must_fail env FAKE_LINES=2 git rebase --edit-todo &&
		GIT_SEQUENCE_EDITOR="cp todo" git rebase --edit-todo &&
		git rebase --continue
	)
'
The second edit complains that commit B is missing even though we have
already pick it. This is because we're using a stale backup file.

Sorry to be the bearer of bad tidings

Phillip

> +		return -4;
> +	} else {
> +		todo_list_write_to_file(r, todo_list, todo_backup, shortrevisions, shortonto,
> +					-1, flags | TODO_LIST_SHORTEN_IDS | TODO_LIST_APPEND_TODO_HELP);
> +	}
>   
>   	return 0;
>   }
> @@ -189,11 +209,27 @@ int todo_list_check(struct todo_list *old_todo, struct todo_list *new_todo)
>   		"the level of warnings.\n"
>   		"The possible behaviours are: ignore, warn, error.\n\n"));
>   
> +	fprintf(stderr, _(edit_todo_list_advice));
> +
>   leave_check:
>   	clear_commit_seen(&commit_seen);
>   	return res;
>   }
>   
> +int todo_list_check_against_backup(struct repository *r, struct todo_list *todo_list)
> +{
> +	struct todo_list backup = TODO_LIST_INIT;
> +	int res = 0;
> +
> +	if (strbuf_read_file(&backup.buf, rebase_path_todo_backup(), 0) > 0) {
> +		todo_list_parse_insn_buffer(r, backup.buf.buf, &backup);
> +		res = todo_list_check(&backup, todo_list);
> +	}
> +
> +	todo_list_release(&backup);
> +	return res;
> +}
> +
>   int check_todo_list_from_file(struct repository *r)
>   {
>   	struct todo_list old_todo = TODO_LIST_INIT, new_todo = TODO_LIST_INIT;
> @@ -212,10 +248,10 @@ int check_todo_list_from_file(struct repository *r)
>   	res = todo_list_parse_insn_buffer(r, old_todo.buf.buf, &old_todo);
>   	if (!res)
>   		res = todo_list_parse_insn_buffer(r, new_todo.buf.buf, &new_todo);
> -	if (!res)
> -		res = todo_list_check(&old_todo, &new_todo);
>   	if (res)
>   		fprintf(stderr, _(edit_todo_list_advice));
> +	if (!res)
> +		res = todo_list_check(&old_todo, &new_todo);
>   out:
>   	todo_list_release(&old_todo);
>   	todo_list_release(&new_todo);
> diff --git a/rebase-interactive.h b/rebase-interactive.h
> index 5f41bf5a28..4af0c1fcc7 100644
> --- a/rebase-interactive.h
> +++ b/rebase-interactive.h
> @@ -11,7 +11,10 @@ void append_todo_help(unsigned keep_empty, int command_count,
>   int edit_todo_list(struct repository *r, struct todo_list *todo_list,
>   		   struct todo_list *new_todo, const char *shortrevisions,
>   		   const char *shortonto, unsigned flags);
> +
>   int todo_list_check(struct todo_list *old_todo, struct todo_list *new_todo);
> +int todo_list_check_against_backup(struct repository *r,
> +				   struct todo_list *todo_list);
>   
>   int check_todo_list_from_file(struct repository *r);
>   
> diff --git a/sequencer.c b/sequencer.c
> index 181bb35f5f..2ff18943fb 100644
> --- a/sequencer.c
> +++ b/sequencer.c
> @@ -57,6 +57,8 @@ static GIT_PATH_FUNC(rebase_path, "rebase-merge")
>   GIT_PATH_FUNC(rebase_path_todo, "rebase-merge/git-rebase-todo")
>   GIT_PATH_FUNC(rebase_path_todo_backup, "rebase-merge/git-rebase-todo.backup")
>   
> +GIT_PATH_FUNC(rebase_path_dropped, "rebase-merge/dropped")
> +
>   /*
>    * The rebase command lines that have already been processed. A line
>    * is moved here when it is first handled, before any associated user
> @@ -4273,6 +4275,14 @@ int sequencer_continue(struct repository *r, struct replay_opts *opts)
>   	if (is_rebase_i(opts)) {
>   		if ((res = read_populate_todo(r, &todo_list, opts)))
>   			goto release_todo_list;
> +
> +		if (file_exists(rebase_path_dropped())) {
> +			if ((res = todo_list_check_against_backup(r, &todo_list)))
> +				goto release_todo_list;
> +
> +			unlink(rebase_path_dropped());
> +		}
> +
>   		if (commit_staged_changes(r, opts, &todo_list))
>   			return -1;
>   	} else if (!file_exists(get_todo_path(opts)))
> @@ -4986,12 +4996,6 @@ int todo_list_write_to_file(struct repository *r, struct todo_list *todo_list,
>   	return res;
>   }
>   
> -static const char edit_todo_list_advice[] =
> -N_("You can fix this with 'git rebase --edit-todo' "
> -"and then run 'git rebase --continue'.\n"
> -"Or you can abort the rebase with 'git rebase"
> -" --abort'.\n");
> -
>   /* skip picking commits whose parents are unchanged */
>   static int skip_unnecessary_picks(struct repository *r,
>   				  struct todo_list *todo_list,
> @@ -5089,11 +5093,7 @@ int complete_action(struct repository *r, struct replay_opts *opts, unsigned fla
>   		todo_list_release(&new_todo);
>   
>   		return error(_("nothing to do"));
> -	}
> -
> -	if (todo_list_parse_insn_buffer(r, new_todo.buf.buf, &new_todo) ||
> -	    todo_list_check(todo_list, &new_todo)) {
> -		fprintf(stderr, _(edit_todo_list_advice));
> +	} else if (res == -4) {
>   		checkout_onto(r, opts, onto_name, &onto->object.oid, orig_head);
>   		todo_list_release(&new_todo);
>   
> diff --git a/sequencer.h b/sequencer.h
> index 75ddc5db3a..00debf5107 100644
> --- a/sequencer.h
> +++ b/sequencer.h
> @@ -11,6 +11,7 @@ const char *git_path_commit_editmsg(void);
>   const char *git_path_seq_dir(void);
>   const char *rebase_path_todo(void);
>   const char *rebase_path_todo_backup(void);
> +const char *rebase_path_dropped(void);
>   
>   #define APPEND_SIGNOFF_DEDUP (1u << 0)
>   
> diff --git a/t/t3404-rebase-interactive.sh b/t/t3404-rebase-interactive.sh
> index 29a35840ed..f5c3da33bf 100755
> --- a/t/t3404-rebase-interactive.sh
> +++ b/t/t3404-rebase-interactive.sh
> @@ -1343,6 +1343,115 @@ test_expect_success 'rebase -i respects rebase.missingCommitsCheck = error' '
>   	test B = $(git cat-file commit HEAD^ | sed -ne \$p)
>   '
>   
> +test_expect_success 'rebase --edit-todo respects rebase.missingCommitsCheck = ignore' '
> +	test_config rebase.missingCommitsCheck ignore &&
> +	rebase_setup_and_clean missing-commit &&
> +	(
> +		set_fake_editor &&
> +		FAKE_LINES="break 1 2 3 4 5" git rebase -i --root &&
> +		FAKE_LINES="1 2 3 4" git rebase --edit-todo &&
> +		git rebase --continue 2>actual
> +	) &&
> +	test D = $(git cat-file commit HEAD | sed -ne \$p) &&
> +	test_i18ngrep \
> +		"Successfully rebased and updated refs/heads/missing-commit" \
> +		actual
> +'
> +
> +test_expect_success 'rebase --edit-todo respects rebase.missingCommitsCheck = warn' '
> +	cat >expect <<-EOF &&
> +	error: invalid line 1: badcmd $(git rev-list --pretty=oneline --abbrev-commit -1 master~4)
> +	Warning: some commits may have been dropped accidentally.
> +	Dropped commits (newer to older):
> +	 - $(git rev-list --pretty=oneline --abbrev-commit -1 master)
> +	 - $(git rev-list --pretty=oneline --abbrev-commit -1 master~4)
> +	To avoid this message, use "drop" to explicitly remove a commit.
> +	EOF
> +	head -n4 expect >expect.2 &&
> +	tail -n1 expect >>expect.2 &&
> +	tail -n4 expect.2 >expect.3 &&
> +	test_config rebase.missingCommitsCheck warn &&
> +	rebase_setup_and_clean missing-commit &&
> +	(
> +		set_fake_editor &&
> +		test_must_fail env FAKE_LINES="bad 1 2 3 4 5" \
> +			git rebase -i --root &&
> +		cp .git/rebase-merge/git-rebase-todo.backup orig &&
> +		FAKE_LINES="2 3 4" git rebase --edit-todo 2>actual.2 &&
> +		head -n6 actual.2 >actual &&
> +		test_i18ncmp expect actual &&
> +		cp orig .git/rebase-merge/git-rebase-todo &&
> +		FAKE_LINES="1 2 3 4" git rebase --edit-todo 2>actual.2 &&
> +		head -n4 actual.2 >actual &&
> +		test_i18ncmp expect.3 actual &&
> +		git rebase --continue 2>actual
> +	) &&
> +	test D = $(git cat-file commit HEAD | sed -ne \$p) &&
> +	test_i18ngrep \
> +		"Successfully rebased and updated refs/heads/missing-commit" \
> +		actual
> +'
> +
> +test_expect_success 'rebase --edit-todo respects rebase.missingCommitsCheck = error' '
> +	cat >expect <<-EOF &&
> +	error: invalid line 1: badcmd $(git rev-list --pretty=oneline --abbrev-commit -1 master~4)
> +	Warning: some commits may have been dropped accidentally.
> +	Dropped commits (newer to older):
> +	 - $(git rev-list --pretty=oneline --abbrev-commit -1 master)
> +	 - $(git rev-list --pretty=oneline --abbrev-commit -1 master~4)
> +	To avoid this message, use "drop" to explicitly remove a commit.
> +
> +	Use '\''git config rebase.missingCommitsCheck'\'' to change the level of warnings.
> +	The possible behaviours are: ignore, warn, error.
> +
> +	You can fix this with '\''git rebase --edit-todo'\'' and then run '\''git rebase --continue'\''.
> +	Or you can abort the rebase with '\''git rebase --abort'\''.
> +	EOF
> +	tail -n11 expect >expect.2 &&
> +	head -n3 expect.2 >expect.3 &&
> +	tail -n7 expect.2 >>expect.3 &&
> +	test_config rebase.missingCommitsCheck error &&
> +	rebase_setup_and_clean missing-commit &&
> +	(
> +		set_fake_editor &&
> +		test_must_fail env FAKE_LINES="bad 1 2 3 4 5" \
> +			git rebase -i --root &&
> +		cp .git/rebase-merge/git-rebase-todo.backup orig &&
> +		test_must_fail env FAKE_LINES="2 3 4" \
> +			git rebase --edit-todo 2>actual &&
> +		test_i18ncmp expect actual &&
> +		test_must_fail git rebase --continue 2>actual &&
> +		test_i18ncmp expect.2 actual &&
> +		test_must_fail git rebase --edit-todo &&
> +		cp orig .git/rebase-merge/git-rebase-todo &&
> +		test_must_fail env FAKE_LINES="1 2 3 4" \
> +			git rebase --edit-todo 2>actual &&
> +		test_i18ncmp expect.3 actual &&
> +		test_must_fail git rebase --continue 2>actual &&
> +		test_i18ncmp expect.3 actual &&
> +		cp orig .git/rebase-merge/git-rebase-todo &&
> +		FAKE_LINES="1 2 3 4 drop 5" git rebase --edit-todo &&
> +		git rebase --continue 2>actual
> +	) &&
> +	test D = $(git cat-file commit HEAD | sed -ne \$p) &&
> +	test_i18ngrep \
> +		"Successfully rebased and updated refs/heads/missing-commit" \
> +		actual
> +'
> +
> +test_expect_success 'rebase.missingCommitsCheck = error after resolving conflicts' '
> +	test_config rebase.missingCommitsCheck error &&
> +	(
> +		set_fake_editor &&
> +		FAKE_LINES="drop 1 break 2 3 4" git rebase -i A E
> +	) &&
> +	git rebase --edit-todo &&
> +	test_must_fail git rebase --continue &&
> +	echo x >file1 &&
> +	git add file1 &&
> +	git rebase --continue
> +'
> +
>   test_expect_success 'respects rebase.abbreviateCommands with fixup, squash and exec' '
>   	rebase_setup_and_clean abbrevcmd &&
>   	test_commit "first" file1.txt "first line" first &&
>