[PATCH 1/2] git-jump: always specify column 1 for diff entries

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>
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 contrib/git-jump/git-jump | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)