Re: [PATCH 7/8] checkout: allow ignoring unmatched pathspec

[Elijah Newren <newren@gmail.com>]

On Sun, Dec 9, 2018 at 12:05 PM Thomas Gummerer <t.gummerer@gmail.com> wrote:
>
> Currently when 'git checkout -- <pathspec>...' is invoked with
> multiple pathspecs, where one or more of the pathspecs don't match
> anything, checkout errors out.
>
> This can be inconvenient in some cases, such as when using git
> checkout from a script.  Introduce a new --ignore-unmatched option,
> which which allows us to ignore a non-matching pathspec instead of
> erroring out.
>
> In a subsequent commit we're going to start using 'git checkout' in
> 'git stash' and are going to make use of this feature.

This makes sense, but seems incomplete.  But to explain it, I think
there's another bug I need to demonstrate first because it's related
on builds on it.  First, the setup:

  $ echo foo >subdir/newfile
  $ git add subdir/newfile
  $ echo bar >>subdir/newfile
  $ git status
  On branch A
  Changes to be committed:
    (use "git reset HEAD <file>..." to unstage)

      new file:   subdir/newfile

  Changes not staged for commit:
    (use "git add <file>..." to update what will be committed)
    (use "git checkout -- <file>..." to discard changes in working directory)

      modified:   subdir/newfile

Now, does it do what we expect?

  $ git checkout HEAD -- subdir/newfile
  error: pathspec 'subdir/newfile' did not match any file(s) known to git

This is the old overlay behavior; kinda lame, but you made no claims
about fixing the default behavior.  What about with your new option?

  $ git checkout --no-overlay HEAD -- subdir
  $ git status
  On branch A
  nothing to commit, working tree clean

Yes, the feature seems to work as advertised.  However, let's try
again with a different variant:

  $ echo foo >subdir/newfile
  $ git checkout --no-overlay HEAD -- subdir
  $ git status
  On branch A
  Untracked files:
    (use "git add <file>..." to include in what will be committed)

      subdir/newfile

Why is the file ignored and left there?  Also:

  $ git checkout --no-overlay HEAD -- subdir/newfile
  error: pathspec 'subdir/newfile' did not match any file(s) known to git

That seems wrong to me.  The point of no-overlay is to make it match
HEAD, and while subdir/newfile doesn't exist in HEAD or the index it
does match in the working tree so the intent is clear. But let's say
that the user did go ahead and specify your new flag:


  $ git checkout --no-overlay --ignore-unmatch HEAD -- subdir/newfile
  $ git status
  On branch A
  Untracked files:
    (use "git add <file>..." to include in what will be committed)

      subdir/newfile

  nothing added to commit but untracked files present (use "git add" to track)

So now it avoids erroring out when the user does more work than
necessary, but it still misses appropriately cleaning up the file.