From c7630fc00b715b77da18ed5f041860e4241b3291 Mon Sep 17 00:00:00 2001
From: Kai Hoewelmeyer <kai@hoewelmeyer.eu>
Date: Sun, 10 Sep 2023 19:00:32 +0200
Subject: [PATCH] fix(nvim): fzf git log on fugitive special commit

Fixes: #651
---
 nvim/config--nvim--init.vim.symlink |  7 ++++++
 nvim/tests/fzf-git.test.vim         | 35 ++++++++++++++++++++++++++---
 2 files changed, 39 insertions(+), 3 deletions(-)

diff --git a/nvim/config--nvim--init.vim.symlink b/nvim/config--nvim--init.vim.symlink
index 8df4c87104..1987c45c15 100644
--- a/nvim/config--nvim--init.vim.symlink
+++ b/nvim/config--nvim--init.vim.symlink
@@ -270,6 +270,13 @@ function commit_and_path()
   if parsed[2] ~= '' then -- we parsed a fugitive:// url
     local commit, path = unpack(vim.fn.split(parsed[1], ':'))
 
+    if string.match(commit, "^[0-3]$") then -- special fugitive commit
+      -- Reset to HEAD to match fugitive's gclog function's behavior.
+      -- There is no obvious, public function to restore the actual commit hash from.
+      -- For "0", there would not be a matching commit hash (other than HEAD anyhow).
+      commit = "HEAD"
+    end
+
     local worktree = vim.fn.FugitiveWorkTree()
     local abs_path = path and worktree .. '/' .. path or worktree
     return {commit or "HEAD", abs_path}
diff --git a/nvim/tests/fzf-git.test.vim b/nvim/tests/fzf-git.test.vim
index 030eef2979..3b86d95fc2 100644
--- a/nvim/tests/fzf-git.test.vim
+++ b/nvim/tests/fzf-git.test.vim
@@ -457,7 +457,7 @@ function Test_CopiedFileFollow()
   call assert_match('firstfile$', bufname(), 'Wrong file name (copied-from)')
 endfunction
 
-function Check_DifferentPwd(id)
+function Check_Preview(id)
   call WaitForFzfResults(1)
 
   call WaitForScreenContent('Author:\|fatal:')
@@ -486,15 +486,44 @@ function Test_DifferentPwd()
   " English language necessary to check for "fatal:" and "Author:" strings
   call setenv('LC_ALL', 'en_US.UTF8')
 
-  call timer_start(50, funcref('Check_DifferentPwd'))
+  call timer_start(50, funcref('Check_Preview'))
   call feedkeys(',gl', 'tx!')
 
   " Explicitly use the HEAD version of the 'firstfile'
   Gedit HEAD:%
 
-  call timer_start(50, funcref('Check_DifferentPwd'))
+  call timer_start(50, funcref('Check_Preview'))
   call feedkeys(',gl', 'tx!')
 
+  " Explicitly use the staging version of the 'firstfile'
+  Gedit :0:%
+
+  call timer_start(50, funcref('Check_Preview'))
+  call feedkeys(',gl', 'tx!')
+endfunction
+
+" showing commit history of a buffer should still working on the staging
+" / etc. buffers that are extensions in fugitive with ":0", ":1", ":2", ":3"
+" Since those are not properly integrated in fugitive as well (e.g., copying
+" the commit hash with "y ctrl-g" leaves the special hashes unresolved.
+" Moreover, "0" references the staging area, which by design has no hash
+" associated.
+function Test_SpecialCommit()
+  call CdTestDir()
+
+  call RunSystemCommand(['git', 'init'])
+  call assert_equal(0, writefile(['something', 'something2', 'something3'], 'firstfile'))
+  call RunSystemCommand(['git', 'add', 'firstfile'])
+  call RunSystemCommand(['git', 'commit', '-m', 'first commit', '--no-verify', '--no-gpg-sign'])
+
+  edit firstfile
+  Gedit :0:%
+
+  " English language necessary to check for "fatal:" and "Author:" strings
+  call setenv('LC_ALL', 'en_US.UTF8')
+
+  call timer_start(50, funcref('Check_Preview'))
+  call feedkeys(',gl', 'tx!')
 endfunction
 
 function Test()