Re: Can git tell me which uncommitted files clash with the incoming changes?

On Mon, Dec 17 2018, Jeff King wrote:

On Mon, Dec 17, 2018 at 08:08:49AM -0500, Mark Kharitonov wrote:

quoted

    C:\Dayforce\test [master ↓2 +0 ~2 -0 !]> git pull
    error: Your local changes to the following files would be
overwritten by merge:
            2.txt
    Please commit your changes or stash them before you merge.
    Aborting
    Updating 2dc8bd0..ea343f8
    C:\Dayforce\test [master ↓2 +0 ~2 -0 !]>

Does git have a command that can tell me which uncommitted files cause
the this error? I can see them displayed by git pull, but I really do
not want to parse git pull output.

That message is generated by merge-recursive, I believe after it's
figured out which files would need to be touched.

I don't offhand know of a way to get that _exact_ answer from another
plumbing command. But in practice it would probably be reasonable to ask
for the diff between your current branch and what you plan to merge, and
cross-reference that with the list of files with local changes.

Something like:

  git pull ;# this fails, but FETCH_HEAD is left over

  git diff-tree -z --name-only HEAD FETCH_HEAD >one
  git diff-index -z --name-only HEAD >two
  comm -z -12 one two

would work on Linux, but "comm -z" is not portable (and I suspect you
may not have comm at all on Windows). You can probably find a way to
show the common elements of the two lists using the scripting language
of your choice.

The answer that gives will be overly broad (e.g., in a case where our
local branch had touched file "foo" but other side had not, we'd
consider "foo" as a difference the two-point diff-tree, whereas a real
3-way merge would realize that we'd keep our version of "foo"). But it
might be good enough for your purposes.

Isn't this done more simply with just running the merge with
git-merge-tree? Maybe I'm missing something. E.g. earlier I had a
conflict between a WIP series of mine in next in
parse-options-cb.c. Just using git-merge-tree and grepping for conflict
markers gives me what conflicted:

    $ git merge-tree origin/master unconditional-abbrev-2 origin/next|grep -E -e '^(merged|changed in both|  (base|our|their|result))' -e '^\+======='
    [...]
    merged
      result 100644 d70c6d9afb94c77c285fe8ee3237f7a40867157a packfile.h
      our    100644 6c4037605d0dfee59a084c440506f1af11708d63 packfile.h
    changed in both
      base   100644 8c9edce52f63bcb1085b119b3a2264a97b1fb374 parse-options-cb.c
      our    100644 1afc11a9901dba25dc0f6151e5d9a7654b6e3192 parse-options-cb.c
      their  100644 e2f3eaed072f77d63890ec814d810199f57248d5 parse-options-cb.c
    +=======
    [...]

Or more simply, you can "grep -q" for '^\+=======' to ask "does this
conflict?".