Re: Problem with git diff

From: Elijah Newren <newren@gmail.com>
Date: Jul 9, 2019, 23:13 UTC
Message-ID: <CABPp-BE1fQs99ipi9Y8gfQO3QHkxzQhn1uriEbj6YjdYH839eQ@mail.gmail.com>
In-Reply-To: <1288734232ea45e0be655668ac60d98f@ASGEXCPWP07.ga.com>

Hi John,

On Tue, Jul 9, 2019 at 3:57 PM McRoberts, John <John.McRoberts@ga.com> wrote:

Show 43 quoted lines

>
> I am responsible for generating a list of all files changed between two
> successive releases of software. I was using 'git diff' but have run into a
> problem.
>
> Consider the following situation: A development branch comes off of commit A
> and files are changed three times.  A tag (REL1) is placed on the third
> commit.  Then the branch is merged back to master.  At this point, master's
> HEAD is at C (and it remains there).  Two development branches are created
> off of master, the first of which is not important here.  In the second one,
> there are files changed and a tag (REL2) applied.
>
>
> ---------------------[I]
>
> /      {dev branch}
>
> /
>
> /
>              {master branch}
> /
>  [A] ---------------------------------[B]------------------------------->[C]
> master <HEAD>
>    \                               filelist 6                           /  \
>     \                                                                  /
> \
>      \                                                                /
> \
>       \                                                              /
> \
>        \                {development branch}                        /
> \
>         \------->[D]----------------------->[E]-------------------[F]
> \------[G]--------[H]
>                                                                  REL1
> REL2
>                 fileset 1               fileset 2           fileset 3
> fileset 4    fileset 5
>
> At this point, I run
>     'git diff  -m --first-parent --pretty=fuller --decorate=short
> --name-only REL2..REL2'

Wow, we really, really need to throw errors and warnings when people use crazy range operators with diff.[1][2] What version of git are you using that accepts --decorate=short as an argument to `git diff`? And why in the world does git diff accept --first-parent or --pretty=fuller?!? That's insane for git-diff to swallow that. (#leftoverbits?) Also, I think you meant `REL1` one of the two times you wrote `REL2`, which makes me suspect you may have done some copy-edit-paste and didn't try this actual command.

Show 5 quoted lines

> I expect to see only filesets 4 and 5 listed.  I also see filesets 1, 2 and
> 3 showing up.  This means that the git diff command is showing files that,in
> fact, did not change between the two tags.  By the way, I verified with a
> file by file comparison that under REL2 and REL1, the files represented by
> filesets 1, 2 and 3 had identical contents.

From your description, I assume you actually ran something like
  git diff --name-only REL1..REL2

which compares REL2 to the merge base of REL1 and REL2 (yes, this is
totally counter-intuitive to a large percentage of the git userbase,
but it is well documented and hard to change).  Also from your
description, what you seem to want is
  git diff --name-only REL1 REL2

since you want to compare the two endpoints.  Does that help get what you want?

Hope that helps, Elijah

[1] https://public-inbox.org/git/CABPp-BECj___HneAYviE3SB=wU6OTcBi3S=+Un1sP6L4WJ7agA@mail.gmail.com/ [2] https://public-inbox.org/git/CABPp-BGg_iSx3QMc-J4Fov97v9NnAtfxZGMrm3WfrGugOThjmA@mail.gmail.com/