Re: Diffing submodule does not yield complete logs for merge commits

On Mon, May 4, 2015 at 2:32 PM, Jens Lehmann [off-list ref] wrote:

Am 04.05.2015 um 17:05 schrieb Robert Dailey:

quoted

On Fri, May 1, 2015 at 12:57 PM, Heiko Voigt [off-list ref] wrote:

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Hi,

On Wed, Apr 29, 2015 at 03:53:11PM -0500, Robert Dailey wrote:

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I am attempting to diff a submodule modified in my working copy and
the only difference is a merge commit. However, I do not get the
"full" range of commits introduced by the merge commit when I diff it:

$ git diff --submodule=log Core
Submodule Core 8b4ec60..def2f3b:
   > Merge remote-tracking branch 'origin/master-ah3k'

However if I go inside my submodule and run `git log` by hand, I get
more information about the TRUE commits introduced:

$ git log --oneline 8b4ec60..def2f3b
def2f3b Merge remote-tracking branch 'origin/master-ah3k'
015c961 Remove log spam in FontManager
7713ba1 Update third party submodule to latest
10aac78 Merge pull request #9 in FE/core from
feature/FE-1348-selecting-continue-on-zero-balance to master-ah3k
287882f FE-1376 Nedd to remain in check detail screen when selecting
donation after SBI
a5a6bed Do not overwrite the current check# within loop
dfb8547 Adding list of checks to CRspChecks before saving
1be280a FE-1354: Guest logged out in specific multiple check scenario
de06d5a [FE-1348] Fix PATT exit while checks still open

It's almost as if the `git diff --submodule=log` approach is passing
in --first-parent to git log, which would exclude commits in the range
that I'm seeing when I run git log manually.

That is exactly the case. In prepare_submodule_summary() that option is
set before doing the revision walk.

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Is this by design? Is there a way to enable the full log history with
`git diff` on a submodule?

This stems from the first implementation for showing submodule diffs in
commit 752c0c24. I guess this was done deliberately to limit the amount
of output you get for a submodule. At the moment this is hardcoded but I
think there is nothing wrong with adding another option to include the
full log.

Cheers Heiko

I will go ahead and work on this feature. Here is what I'd like to see:

1. `git diff --submodule` should have the ability to display full logs
vs current logs (i.e. without --first-parent)

I agree. Just recently I started missing that feature too at $DAYJOB.

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2. `git submodule summary` should have an option to display full logs
or "first-parent" logs.

No objection against that. Maybe now is a good time to make `git
submodule summary` use `git diff --submodule` internally to make
them behave the same?

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For #1, do you recommend adding a 3rd setting for `diff.submodule`
config? Something like "full-log" or something? Or an entirely new
config?

I'd go with a 3rd setting for diff.submodule (and "full-log" would
have been my first choice too ;-).

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I noticed that in diff.h, the DIFF_OPT flags already consume

31 bits. If this is a 32-bit flag, there is only 1 bit left. If we go
with a 3rd setting for `diff.submodule` I think this might consume the
last bit.

Yup. But I'm not sure we can do anything about it.

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We could also make `git diff --submodule` default to the "full log"
type, and if users want only first parent logs in submodule summary,
they'd have to execute `git submodule summary` instead.

Please do not change defaults that people lived fine with for years
lightly. But I won't object changing that on a major version if a
majority of users request that.

Since I am not a linux user, I have implemented this feature against
the Git for Windows fork of git. I am not able to verify changes if I
make them directly against the Git repository. Is it OK if you guys
end up getting this as an upstream patch later from that project? Also
I am not familiar with the bash unit tests, I will need help with
that.