[RFC] prefix_path: show gitdir when arg is outside repo

Commit Message

Emily Shaffer Feb. 14, 2020, 11:29 p.m. UTC

From: Emily Shaffer <[e-mail]>

When developing a script, it can be painful to understand why Git thinks
something is outside the current repo, if the current repo isn't what
the user thinks it is. Since this can be tricky to diagnose, especially
in cases like submodules or nested worktrees, let's give the user a hint
about which repository is offended about that path.

Signed-off-by: Emily Shaffer <[e-mail]>
---
This one comes from a user feature request. This user is running some
Git client commands on a build machine somewhere and finding it hard to
reason about the cause of the "outside repo" error.

I see two arguments:

For:
 - A user checking their own `pwd` might still not come to the same
   conclusion Git does about the current repo, if their filesystem is in
   some weird state
 - This warning is intended for human eyes (die(), stderr) so it's reasonable
   to give some info to make the human's life easier

Against:
 - It's chatty, especially given the absolute directory. This may be a
   pretty common mistake ('git add' with thumbfingers?) so it could be
   chatty, frequently - not great.
   (Sidebar: Just including the relative directory is really not very
   useful - since you're still left thinking, "relative to where?")

I also dug around a little to see whether I could consolidate the
pathspec.c logic, which is nearly identical to setup.c, into another
helper in setup.c (a la prefix_path_1()). But since the die() message is
somewhat different, and init_pathspec_item() is the _only_ place which
uses prefix_path_gently() in this way, it wasn't feasible. (The other
caller of prefix_path_gently() is immediately below prefix_path(), and
doesn't die at all, print errors, or capture out-params from
prefix_path_gently().)

 - Emily

 pathspec.c | 3 ++-
 setup.c    | 3 ++-
 2 files changed, 4 insertions(+), 2 deletions(-)

Comments

brian m. carlson Feb. 15, 2020, 12:02 a.m. UTC | #1

On 2020-02-14 at 23:29:33, [e-mail] wrote:
> From: Emily Shaffer <[e-mail]>
> 
> When developing a script, it can be painful to understand why Git thinks
> something is outside the current repo, if the current repo isn't what
> the user thinks it is. Since this can be tricky to diagnose, especially
> in cases like submodules or nested worktrees, let's give the user a hint
> about which repository is offended about that path.
> 
> Signed-off-by: Emily Shaffer <[e-mail]>
> ---
> This one comes from a user feature request. This user is running some
> Git client commands on a build machine somewhere and finding it hard to
> reason about the cause of the "outside repo" error.
> 
> I see two arguments:
> 
> For:
>  - A user checking their own `pwd` might still not come to the same
>    conclusion Git does about the current repo, if their filesystem is in
>    some weird state
>  - This warning is intended for human eyes (die(), stderr) so it's reasonable
>    to give some info to make the human's life easier
> 
> Against:
>  - It's chatty, especially given the absolute directory. This may be a
>    pretty common mistake ('git add' with thumbfingers?) so it could be
>    chatty, frequently - not great.
>    (Sidebar: Just including the relative directory is really not very
>    useful - since you're still left thinking, "relative to where?")

I'm very much in favor of this patch.  I recently ran into a similar
problem with Git LFS with path canonicalization and having both paths in
the error message made it immediately obvious what the problem was.

> diff --git a/pathspec.c b/pathspec.c
> index 128f27fcb7..5d661df5cf 100644
> --- a/pathspec.c
> +++ b/pathspec.c
> @@ -439,7 +439,8 @@ static void init_pathspec_item(struct pathspec_item *item, unsigned flags,
>  		match = prefix_path_gently(prefix, prefixlen,
>  					   &prefixlen, copyfrom);
>  		if (!match)
> -			die(_("%s: '%s' is outside repository"), elt, copyfrom);
> +			die(_("%s: '%s' is outside repository at '%s'"), elt,
> +			    copyfrom, absolute_path(get_git_dir()));

Do we want the top level directory in these two spots instead of the git
directory?  I suspect that might be more helpful, since it looks like
we're dealing with working tree files.

Emily Shaffer Feb. 15, 2020, 12:46 a.m. UTC | #2

On Sat, Feb 15, 2020 at 12:02:30AM +0000, brian m. carlson wrote:
> On 2020-02-14 at 23:29:33, [e-mail] wrote:
> > From: Emily Shaffer <[e-mail]>
> > 
> > When developing a script, it can be painful to understand why Git thinks
> > something is outside the current repo, if the current repo isn't what
> > the user thinks it is. Since this can be tricky to diagnose, especially
> > in cases like submodules or nested worktrees, let's give the user a hint
> > about which repository is offended about that path.
> > 
> > Signed-off-by: Emily Shaffer <[e-mail]>
> > ---
> > This one comes from a user feature request. This user is running some
> > Git client commands on a build machine somewhere and finding it hard to
> > reason about the cause of the "outside repo" error.
> > 
> > I see two arguments:
> > 
> > For:
> >  - A user checking their own `pwd` might still not come to the same
> >    conclusion Git does about the current repo, if their filesystem is in
> >    some weird state
> >  - This warning is intended for human eyes (die(), stderr) so it's reasonable
> >    to give some info to make the human's life easier
> > 
> > Against:
> >  - It's chatty, especially given the absolute directory. This may be a
> >    pretty common mistake ('git add' with thumbfingers?) so it could be
> >    chatty, frequently - not great.
> >    (Sidebar: Just including the relative directory is really not very
> >    useful - since you're still left thinking, "relative to where?")
> 
> I'm very much in favor of this patch.  I recently ran into a similar
> problem with Git LFS with path canonicalization and having both paths in
> the error message made it immediately obvious what the problem was.
> 
> > diff --git a/pathspec.c b/pathspec.c
> > index 128f27fcb7..5d661df5cf 100644
> > --- a/pathspec.c
> > +++ b/pathspec.c
> > @@ -439,7 +439,8 @@ static void init_pathspec_item(struct pathspec_item *item, unsigned flags,
> >  		match = prefix_path_gently(prefix, prefixlen,
> >  					   &prefixlen, copyfrom);
> >  		if (!match)
> > -			die(_("%s: '%s' is outside repository"), elt, copyfrom);
> > +			die(_("%s: '%s' is outside repository at '%s'"), elt,
> > +			    copyfrom, absolute_path(get_git_dir()));
> 
> Do we want the top level directory in these two spots instead of the git
> directory?  I suspect that might be more helpful, since it looks like
> we're dealing with working tree files.

I had considered it, and thought .git directory was less ambiguous,
primarily for the first bullet in the "For" list above - "for some
reason, the .git dir I see isn't the one that Git is coming up with".
The .git dir does have a pointer to the worktree ('gitdir' in the
worktree case and 'config' in the submodule case). Conversely, in both
the submodule and worktree cases the worktree contains a ".git" file
with the path to the gitdir.

I also tried the following:

  $ git clone --separate-git-dir=explicit-gitdir https://github.com/git/git
  explicit-worktree
  $ cd explicit-gitdir
  $ grep -Rn "explicit-worktree"
  <no results>
  $ cd ../explicit-worktree
  $ cat .git
  <absolute path to explicit-gitdir>

So it looks like in the clone with --separate-git-dir case, there's no
way to identify the worktree from the gitdir.

All this to say, on second thought, I think you're right. From the
worktree's top level, the gitdir is consistently findable. From gitdir,
the worktree is not consistently findable.

I'll send a reroll.

 - Emily

> -- 
> brian m. carlson: Houston, Texas, US
> OpenPGP: https://keybase.io/bk2204

Patch

diff --git a/pathspec.c b/pathspec.c
index 128f27fcb7..5d661df5cf 100644
--- a/pathspec.c
+++ b/pathspec.c
@@ -439,7 +439,8 @@  static void init_pathspec_item(struct pathspec_item *item, unsigned flags,
 		match = prefix_path_gently(prefix, prefixlen,
 					   &prefixlen, copyfrom);
 		if (!match)
-			die(_("%s: '%s' is outside repository"), elt, copyfrom);
+			die(_("%s: '%s' is outside repository at '%s'"), elt,
+			    copyfrom, absolute_path(get_git_dir()));
 	}
 
 	item->match = match;
diff --git a/setup.c b/setup.c
index 12228c0d9c..48cc2320cb 100644
--- a/setup.c
+++ b/setup.c
@@ -121,7 +121,8 @@  char *prefix_path(const char *prefix, int len, const char *path)
 {
 	char *r = prefix_path_gently(prefix, len, NULL, path);
 	if (!r)
-		die(_("'%s' is outside repository"), path);
+		die(_("'%s' is outside repository at '%s'"), path,
+		    absolute_path(get_git_dir()));
 	return r;
 }