Output of 'diff' and 'diff --raw' not the same for modified submodule

Tim Henigan· Apr 4, 2012, 13:03 UTC · lore

If a submodule has new commits, then 'git diff' and 'git diff --raw' report different outputs.

For example, the following output is given after adding a new commit to a submodule:

$ git version git version 1.7.10.rc4

$ git diff

diff --git a/lib/tst-mergetool b/lib/tst-mergetool
index 9917ea0..5bc1908 160000
--- a/lib/tst-mergetool
+++ b/lib/tst-mergetool
@@ -1 +1 @@
-Subproject commit 9917ea0c228a0c24153da38df954f8a9d78cafac
+Subproject commit 5bc19083c436aaa85762cdc309e62ed98f5cc276

$ git diff --raw --no-abbrev
:160000 160000 9917ea0c228a0c24153da38df954f8a9d78cafac
0000000000000000000000000000000000000000 M  lib/tst-mergetool


'git diff' shows the new SHA1 for the submodule, but 'git diff --raw'
shows the NULL ID.  From the diff man page, I understand that the NULL
ID indicates "creation, unmerged or 'look at the work tree'", but I
expected the output of two commands to match.

Is this the intended behavior?

Thanks,
Tim

Junio C Hamano· Apr 4, 2012, 18:02 UTC · re: Tim Henigan · lore

Re: Output of 'diff' and 'diff --raw' not the same for modified submodule

Tim Henigan <tim.henigan@gmail.com> writes:

> If a submodule has new commits, then 'git diff' and 'git diff --raw'
> report different outputs.

There is nothing different except for the inherent difference between a patch and the row information.

Show 21 quoted lines

> $ git version
> git version 1.7.10.rc4
>
> $ git diff
> diff --git a/lib/tst-mergetool b/lib/tst-mergetool
> index 9917ea0..5bc1908 160000
> --- a/lib/tst-mergetool
> +++ b/lib/tst-mergetool
> @@ -1 +1 @@
> -Subproject commit 9917ea0c228a0c24153da38df954f8a9d78cafac
> +Subproject commit 5bc19083c436aaa85762cdc309e62ed98f5cc276
>
> $ git diff --raw --no-abbrev
> :160000 160000 9917ea0c228a0c24153da38df954f8a9d78cafac
> 0000000000000000000000000000000000000000 M  lib/tst-mergetool
>
>
> 'git diff' shows the new SHA1 for the submodule, but 'git diff --raw'
> shows the NULL ID.  From the diff man page, I understand that the NULL
> ID indicates "creation, unmerged or 'look at the work tree'", but I
> expected the output of two commands to match.

You are fooled by the textual patch output.

Consider "Subproject commit <blah>" a textconv-ed version of what is on that path. Repeat the above but with a regular file at tst-mergetool in both preimage and postimage. You will see exactly the same output. Lines that begin with "-" show the information for the preimage, while those that begin with "+" show the information for the postimage.

The --raw output always uses 0{40} to tell you that you need to look at the working tree for the information you seek for the right hand side (for "U" entries, 0{40} merely means that we do not have any information to show on the unmerged side in the first place), and also to mark that the side that has 0{40} on an "M" entry talks about the working tree.