patch, 2 partsa few git-jump quality-of-life fixes

Here are fixes for some small corner-case annoyances I found using "git-jump diff".

  [1/2]: git-jump: always specify column 1 for diff entries
  [2/2]: git-jump: ignore deleted files in diff mode

 contrib/git-jump/git-jump | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

-Peff

When we generate a quickfix entry for a diff hunk, we provide just the filename and line number along with the content, like:

  file:1: contents of the line

This can be a problem if the line itself looks like a quickfix header. For example (and this is adapted from a real-world case that bit me):

  echo 'static_lease 10:11:12:13:14:15:16 10.0.0.1' >file
  git add file
  echo change >file

produces:

  file:1: static_lease 10:11:12:13:14:15:16 10.0.0.1

which is ambiguous. It could be line 1 of "file", or line 11 of the file "file:1: static_lease 10", and so on. In the case of vim's default config, it seems to prefer the latter (you can configure "errorformat" with a variety of patterns, but out of the box it matches some common ones).

One easy way to fix this is to provide a column number, like:

  file:1:1: static_lease 10:11:12:13:14:15:16 10.0.0.1

which causes vim to prefer line 1 of "file" again (due to the preference order of the various patterns in the default errorformat).

There are other options. For example, at least in my version of vim, wrapping the file in quotation marks like:

  "file":1: static_lease 10:11:12:13:14:15:16 10.0.0.1

also works. That perhaps would the right thing even if you had the silly file name "file:1:1: foo 10". But it's not clear what would happen if you had a filename with quotes in it.

This feature is inherently scraping text, and there's bound to be some ambiguities. I don't think it's worth worrying too much about unlikely filenames, as its the file content that is more likely to introduce unexpected characters.

So let's just go with the extra ":1" column specifier. We know this is supported everywhere, as git-jump's "grep" mode already uses it (and thus doesn't exhibit the same problem).

The "merge" mode is mostly immune to this, as it only matches "<<<<<<<" conflict marker lines. It's possible of course to have a marker that says "foo 10:11" later in the line, but in practice these will only have branches and perhaps file names, so it's probably not worth worrying about (and fixing it would involve passing --column to the system grep, which may not be portable).

I also gave some thought as to whether we could put something more useful than "1" in the column field for diffs. In theory we could find the first changed character of the line, but this is tricky in practice. You'd have to correlate before/after lines of the hunk to decide what changed. So:

  -this is a foo line
  +this is a bar line

is easy (column 11). But:

  -this is a foo line
  +another line
  +this is a bar line

is harder.

This commit certainly doesn't preclude trying to do something more clever later, but it's a much deeper rabbit hole than just fixing the syntactic ambiguity.

Signed-off-by: Jeff King <peff@peff.net>
---
 contrib/git-jump/git-jump | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

On Sun, 15 Sept 2024 at 13:18, Jeff King <peff@peff.net> wrote:

I've never hit this, but it doesn't look too crazy. A couple of digits and a colon and things begin to match. Ok.

Makes sense.

Right. Looking around, I can find someone asking the Internet how to escape the filename and not getting any response.

Agreed. (s/its/it's/)

I suppose we could use `git grep --no-index` instead of `grep` for `git jump merge`. Anyway, that's out of scope here.

Heh. Yes, in theory everything is possible. Your approach makes sense.

Looks good to me and from my testing, this fixes the problem as described.

Martin

If you do something like this:

  rm file_a
  echo change >file_b
  git jump diff

then we'll generate two quickfix entries for the diff, one for each file. But the one for the deleted file is rather pointless. There's no content to show since the file is gone, and in fact we open the editor with the path /dev/null!

In vim, at least, the result is a confusing annoyance: the editor opens with an empty buffer, and you have to skip past it to the useful quickfix entry (after scratching your head and figuring out that no, nothing is broken).

Let's skip such entries entirely. There's nothing useful to show, since the point is that the file has been deleted.

It is possible that you could be doing a diff whose post-image is not the working tree, and then you'd perhaps be jumping to the deleted content (or at least something that was in the same spot). But I don't think it's worth worrying about that case. For one thing, using git-jump for such diffs is a bad idea in general, as it's going to sometimes move you to the wrong spot. And two, a deletion is always going to have one hunk starting at line 1, which is not that interesting to jump to in the first place.

Signed-off-by: Jeff King <peff@peff.net>
---
 contrib/git-jump/git-jump | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

On Sun, 15 Sept 2024 at 13:20, Jeff King <peff@peff.net> wrote:

Ah, yes, I've seen this. I just went "I can see why this would happen" and moved on to the next hunk. Thanks for actually patching.

Agreed. Anybody who relies on `git jump diff` to produce an empty quickfix list (no entries to go through) if *and only if* the diff is empty is already in for a surprise due to binary files. Skipping /dev/null makes perfect sense.

This looks very reasonable. From my testing, this patch fixes the issue.

Martin

On Sun, Sep 15, 2024 at 07:20:24AM -0400, Jeff King wrote:

I was surprised to not see you use `--diff-filter` here, but I think that that makes sense. You only would want to exclude deletions, since that would be the only time the post-image is /dev/null AFAICT.

But I guess that would make it impossible to do "git jump diff --diff-filter", which may be useful in some cases. TBH, I have almost never used --diff-filter myself, so I'm not sure how common that is.

In any event, this seems to be quite a reasonable implementation to me.

Thanks, Taylor

Taylor Blau <me@ttaylorr.com> writes:

So "--diff-filter=d" (lowercase)?

On Tue, Sep 17, 2024 at 08:03:33AM -0700, Junio C Hamano wrote:

Hmm, yeah, I think that probably would work. In my mind, we are accepting arbitrary diffs from the user because of the "$@". But anybody who overrides us with

  git jump diff --diff-filter=D

maybe gets what they want/deserve. I think it's mostly academic, and as the original has already graduated, I'm inclined to leave it unless somebody comes back with some use case.

(Sorry for the slow reply, I am quite behind due to travel last week).

-Peff

On Tue, Sep 24, 2024 at 04:55:58PM -0400, Jeff King wrote:

Yeah, this is definitely all academic. I do not at all mind the implementation that you went with here.

Hopefully your travel back went smoothly. Welcome back :-).

Thanks, Taylor

Taylor Blau <me@ttaylorr.com> writes:

Neither do I.  Thanks, both.