From 8ede0aaf57e1dbb5416ddbe30d0bfdde762e90bf Mon Sep 17 00:00:00 2001
From: Tim Pope <code@tpope.net>
Date: Tue, 6 Apr 2021 23:38:18 -0400
Subject: [PATCH] Provide :GBrowse behavior in blame buffers

If a line number is given, browse to the commit on that line.
Otherwise, browse to the file, same as if called from the original
buffer.

It would probably make more sense to open the corresponding blame page
on providers that support it, but that will have to wait on an API
change.

References https://github.com/tpope/vim-fugitive/issues/1214
---
 autoload/fugitive.vim | 20 +++++++++++++++-----
 1 file changed, 15 insertions(+), 5 deletions(-)

diff --git a/autoload/fugitive.vim b/autoload/fugitive.vim
index 4c39543..c577bd3 100644
--- a/autoload/fugitive.vim
+++ b/autoload/fugitive.vim
@@ -5576,7 +5576,10 @@ endfunction
 
 function! s:BlameCommitFileLnum(...) abort
   let line = a:0 ? a:1 : getline('.')
-  let state = a:0 ? a:2 : s:TempState()
+  let state = a:0 > 1 ? a:2 : s:TempState()
+  if get(state, 'filetype', '') !=# 'fugitiveblame'
+    return ['', '', 0]
+  endif
   let commit = matchstr(line, '^\^\=[?*]*\zs\x\+')
   if commit =~# '^0\+$'
     let commit = ''
@@ -6126,9 +6129,6 @@ function! fugitive#BrowseCommand(line1, count, range, bang, mods, arg, args) abo
     else
       let rev = arg
     endif
-    if rev ==# ''
-      let rev = s:DirRev(@%)[1]
-    endif
     if rev =~? '^\a\a\+:[\/][\/]' && rev !~? '^fugitive:'
       let rev = substitute(rev, '\\\@<![#!]\|\\\@<!%\ze\w', '\\&', 'g')
     elseif rev ==# ':'
@@ -6140,7 +6140,17 @@ function! fugitive#BrowseCommand(line1, count, range, bang, mods, arg, args) abo
     endif
     exe s:DirCheck(dir)
     if empty(expanded)
-      let expanded = s:Relative(':(top)', dir)
+      let bufname = s:BufName('%')
+      let expanded = s:DirRev(bufname)[1]
+      if empty(expanded)
+        let expanded = fugitive#Path(bufname, ':(top)', dir)
+      endif
+      if a:count > 0 && bufname !=# bufname('')
+        let blame = s:BlameCommitFileLnum(getline(a:count))
+        if len(blame[0])
+          let expanded = blame[0]
+        endif
+      endif
     endif
     let cdir = FugitiveVimPath(fugitive#CommonDir(dir))
     for subdir in ['tags/', 'heads/', 'remotes/']