Re: [PATCH 1/2] update-index: optionally leave skip-worktree entries alone

> "Johannes Schindelin via GitGitGadget" <gitgitgadget@gmail.com>
> writes:
>
> > From: Johannes Schindelin <johannes.schindelin@gmx.de>
> >
> > While `git update-index` mostly ignores paths referring to index entries
> > whose skip-worktree bit is set, in b4d1690df11 (Teach Git to respect
> > skip-worktree bit (reading part), 2009-08-20), for reasons that are not
> > entirely obvious, the `--remove` option was made special: it _does_
> > remove index entries even if their skip-worktree bit is set.
>
> I think that made sense to notice removal of the path, because
> skip-worktree bit was not "apply --cached semantics instead of
> looking at the working tree files".  In other words, it was only
> about contents inside the files, and not existence of paths.
>
> I am not offhand sure if it still makes sense; if I were being asked
> to review that commit today, I suspect that I may be tempted to say
> that we should ignore both contents change and presence change for
> entries that have skip-worktree bit set.
>
> > However, in preparation for fixing a bug in `git stash` where it
> > pretends that skip-worktree entries have actually been removed, we need
> > a mode where `git update-index` leaves all skip-worktree entries alone,
> > even if the `--remove` option was passed.
>
> We might want to make this the default eventually (is there a known
> use case where the current behaviour makes sense, I wonder?), but
> I agree that this is a safe thing to do at least for now.
>
> > Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
> > ---
> >  Documentation/git-update-index.txt | 6 ++++++
> >  builtin/update-index.c             | 6 +++++-
> >  2 files changed, 11 insertions(+), 1 deletion(-)
>
> Isn't this something reasonably easy to guard against regression with
> a test or two?

>
> >
> > diff --git a/Documentation/git-update-index.txt b/Documentation/git-update-index.txt
> > index 1c4d146a41..08393445e7 100644
> > --- a/Documentation/git-update-index.txt
> > +++ b/Documentation/git-update-index.txt
> > @@ -16,6 +16,7 @@ SYNOPSIS
> >  	     [--chmod=(+|-)x]
> >  	     [--[no-]assume-unchanged]
> >  	     [--[no-]skip-worktree]
> > +	     [--[no-]ignore-skip-worktree-entries]
> >  	     [--[no-]fsmonitor-valid]
> >  	     [--ignore-submodules]
> >  	     [--[no-]split-index]
> > @@ -113,6 +114,11 @@ you will need to handle the situation manually.
> >  	set and unset the "skip-worktree" bit for the paths. See
> >  	section "Skip-worktree bit" below for more information.
> >
> > +
> > +--[no-]ignore-skip-worktree-entries::
> > +	Do not remove skip-worktree (AKA "index-only") entries even when
> > +	the `--remove` option was specified.
> > +
> >  --[no-]fsmonitor-valid::
> >  	When one of these flags is specified, the object name recorded
> >  	for the paths are not updated. Instead, these options
> > diff --git a/builtin/update-index.c b/builtin/update-index.c
> > index dff2f4b837..074d563df0 100644
> > --- a/builtin/update-index.c
> > +++ b/builtin/update-index.c
> > @@ -35,6 +35,7 @@ static int verbose;
> >  static int mark_valid_only;
> >  static int mark_skip_worktree_only;
> >  static int mark_fsmonitor_only;
> > +static int ignore_skip_worktree_entries;
> >  #define MARK_FLAG 1
> >  #define UNMARK_FLAG 2
> >  static struct strbuf mtime_dir = STRBUF_INIT;
> > @@ -381,7 +382,8 @@ static int process_path(const char *path, struct stat *st, int stat_errno)
> >  		 * so updating it does not make sense.
> >  		 * On the other hand, removing it from index should work
> >  		 */
> > -		if (allow_remove && remove_file_from_cache(path))
> > +		if (!ignore_skip_worktree_entries && allow_remove &&
> > +		    remove_file_from_cache(path))
> >  			return error("%s: cannot remove from the index", path);
> >  		return 0;
> >  	}
> > @@ -1013,6 +1015,8 @@ int cmd_update_index(int argc, const char **argv, const char *prefix)
> >  		{OPTION_SET_INT, 0, "no-skip-worktree", &mark_skip_worktree_only, NULL,
> >  			N_("clear skip-worktree bit"),
> >  			PARSE_OPT_NOARG | PARSE_OPT_NONEG, NULL, UNMARK_FLAG},
> > +		OPT_BOOL(0, "ignore-skip-worktree-entries", &ignore_skip_worktree_entries,
> > +			 N_("do not touch index-only entries")),
> >  		OPT_SET_INT(0, "info-only", &info_only,
> >  			N_("add to index only; do not add content to object database"), 1),
> >  		OPT_SET_INT(0, "force-remove", &force_remove,
>