Bug#928356: elpa-magit: diff buffer when committing is often useless/wrong

[Robbie Harwood <rharwood@club.cc.cmu.edu>]

Package: elpa-magit
Version: 2.90.1-2
Severity: normal

Dear Maintainer,

When committing changes without using staging (i.e., with `git commit -a` or
`git commit explicit/path/to/files`), the magit-diff buffer which is spawned
shows the diff for the most recent commit to master - not the proposed action
of the current commit.  To reproduce:

    git init test
    cd test
    echo "test file" > foo
    git add foo
    git commit -am 'Initial commit'
    echo "something else" > foo
    git commit -a # this will incorrectly show an empty diff buffer
    echo "a third thing" > foo
    git commit -a # this will incorrectly show the previous commit

Thanks,
--Robbie

-- System Information:
Debian Release: buster/sid
  APT prefers testing-debug
  APT policy: (700, 'testing-debug'), (700, 'testing'), (500, 'unstable-debug'), (500, 'unstable'), (300, 'experimental-debug'), (300, 'experimental')
Architecture: amd64 (x86_64)

Kernel: Linux 4.19.0-4-rt-amd64 (SMP w/4 CPU cores; PREEMPT)
Locale: LANG=es_US.UTF-8, LC_CTYPE=es_US.UTF-8 (charmap=UTF-8), LANGUAGE=es_US.UTF-8 (charmap=UTF-8)
Shell: /bin/sh linked to /bin/dash
Init: systemd (via /run/systemd/system)
LSM: AppArmor: enabled

Versions of packages elpa-magit depends on:
ii  elpa-dash         2.14.1+dfsg-1
ii  elpa-ghub         3.2.0-1
ii  elpa-git-commit   2.90.1-2
ii  elpa-magit-popup  2.12.5-1
ii  elpa-with-editor  2.8.1-1
ii  emacsen-common    3.0.4
ii  git               1:2.20.1-2

elpa-magit recommends no packages.

elpa-magit suggests no packages.

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