Re: Re* Bug report: reset -p HEAD

[Jeff King <peff@peff.net>]

On Thu, Oct 24, 2013 at 08:40:13PM -0700, Junio C Hamano wrote:

> Maarten de Vries <maarten@de-vri.es> writes:
> 
> > Some more info: It used to work as intended. Using a bisect shows it
> > has been broken by commit 166ec2e9.
> 
> Thanks.
> 
> A knee-jerk change without thinking what side-effect it has for you
> to try out.
> 
>  builtin/reset.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/builtin/reset.c b/builtin/reset.c
> index f2f9d55..a3088d9 100644
> --- a/builtin/reset.c
> +++ b/builtin/reset.c
> @@ -304,7 +304,10 @@ int cmd_reset(int argc, const char **argv, const char *prefix)
>  	if (patch_mode) {
>  		if (reset_type != NONE)
>  			die(_("--patch is incompatible with --{hard,mixed,soft}"));
> -		return run_add_interactive(sha1_to_hex(sha1), "--patch=reset", &pathspec);
> +		return run_add_interactive(
> +			(unborn || strcmp(rev, "HEAD"))
> +			? sha1_to_hex(sha1)
> +			: "HEAD", "--patch=reset", &pathspec);
>  	}

I think that's the correct fix for the regression.  You are restoring
the original, pre-166ec2e9 behavior for just the HEAD case. I do not
think add--interactive does any other magic between a symbolic rev and
its sha1, except for recognizing HEAD specially. However, if you wanted
to minimize the potential impact of 166ec2e9, you could pass the sha1
_only_ in the unborn case, like this:

diff --git a/builtin/reset.c b/builtin/reset.c
index f2f9d55..bfdd8d3 100644
--- a/builtin/reset.c
+++ b/builtin/reset.c
@@ -283,6 +283,7 @@ int cmd_reset(int argc, const char **argv, const char *prefix)
 	if (unborn) {
 		/* reset on unborn branch: treat as reset to empty tree */
 		hashcpy(sha1, EMPTY_TREE_SHA1_BIN);
+		rev = EMPTY_TREE_SHA1_HEX;
 	} else if (!pathspec.nr) {
 		struct commit *commit;
 		if (get_sha1_committish(rev, sha1))
@@ -304,7 +305,7 @@ int cmd_reset(int argc, const char **argv, const char *prefix)
 	if (patch_mode) {
 		if (reset_type != NONE)
 			die(_("--patch is incompatible with --{hard,mixed,soft}"));
-		return run_add_interactive(sha1_to_hex(sha1), "--patch=reset", &pathspec);
+		return run_add_interactive(rev, "--patch=reset", &pathspec);
 	}
 
 	/* git reset tree [--] paths... can be used to

That fixes any possible regression from add--interactive treating the
two cases differently. On an unborn branch, we will still say "apply
this hunk" rather than "unstage this hunk". That's not a regression,
because it simply didn't work before, but it's not ideal. To fix that,
we need to somehow tell add--interactive "this is HEAD, but use the
empty tree because it's unborn". I can think of a few simple-ish ways:

  1. Pass the head/not-head flag as a separate option.

  2. Pass HEAD even in the unborn case; teach add--interactive to
     convert an unborn HEAD to the empty tree.

  3. Teach add--interactive to recognize the empty tree sha1 as an
     "unstage" path.

I kind of like (3). At first glance, it is wrong; we will also treat
"git reset -p $(git hash-object -t tree /dev/null)" as if "HEAD" had
been passed. But if you are explicitly passing the empty tree like that,
I think saying "unstage" makes a lot of sense.

-Peff