Amend mode does not load the previous message when the edited file was opened from a path outide the repository.

[bonderado]

Short description

When (neo)vim is used to open a tracked file from outside the git repository (e.g.: one directory above), vimagit manages to perform normal commits ('CC') correctly, however, when trying to amend a commit ('CA'), the previous commit message is not loaded.

Steps to reproduce

To reproduce the issue:

1. Setup a test repo typing the following commands:
   $ cd ~
   $ mkdir gitest
   $ cd gitest
   $ git init
   $ mkdir sub
   $ touch readme.txt
   $ git commit -m 'initial commit'

2. get outside the repository and open "readme.txt"
   $ cd ..
   $ nvim readme.txt

3. from within (neo)vim:
   :Magit
   CA

4. Observe the issue

Expected result:
vimagit switches to amend mode and the previous commit message is shown in the 'Commit message' section.

Actual result:
vimagit switches to amend mode, but no text appears in the 'Commit message' section.

The cause seems to be that vimagit executes:
$ git rev-parse --git-dir
in the edited file directory which in this case is the top level of the repository, where the command returns a relative path to the .git directory, that is then stored in "b:magit_git_dir".
Later, when vimagit tries to open the file '.git/COMMIT_EDITMSG', the relative path will point to a non-existing file, since the editor's CWD is "gitest/.." instead of "gitest".

NOTE: opening the file from the top level dir of the repository as in:
$ cd $HOME/gitest
$ nvim readme.txt
would work.

NOTE: runnig the command:
$ git rev-parse --git-dir
in a subfolder of the repository:
$ mkdir sub
$ cd sub
$ git rev-parse --git-dir
would result in an absolute path.

Solution:

Since vimagit invokes
git rev-parse --git-dir
from the path of the edited file, using fnamemodify(git_dir, ':p') would solve the issue, since we are either in the top dir and the relative path is correctly turned to an absolute one, or we are in a subdir and the path is already absolute.

Environment

• neovim version:
  NVIM v0.7.2
  Build type: Release
  LuaJIT 2.1.0-beta3
  Compiled by team+vim@tracker.debian.org

• git version 2.35.1

• current vimagit: 88720f4

• OS: Linux 5.18.0-2-amd64 # 1 SMP PREEMPT_DYNAMIC Debian 5.18.5-1 (2022-06-16) x86_64 GNU/Linux

• both terminal nvim and nvim-qt are affected

[jreybert]

Thanks for such a complete report and for the PR.

I am currently reviving the project, more specifically the CI, which has not been run/updated since github abandoned travis.
I plan to finish this next week.

Your issue seems to be a valid case to be fixed, but it touches fundamental vimagit operations, so I prefer to ensure your fix passes the testsuite.

[jreybert]

requires #202

[bonderado]

In fact, I was a bit surprised at not getting a test-suite result:
by all means, make sure I did not break anything.

Thank you for your work on this marvelous plugin.

[v-slava]

IMHO it is better to use git rev-parse --absolute-git-dir instead of git rev-parse --git-dir.