From bba8d1beb37fe933a9f182b6bdf981e01f31499a Mon Sep 17 00:00:00 2001
From: Tim Pope <code@tpope.net>
Date: Wed, 1 Mar 2023 16:29:16 -0500
Subject: [PATCH] Avoid narrow :Git subcommand splits in blame windows

If commit maps are to made available in blame buffers, then the existing
behavior of editing the commit message in a horizontal split of a narrow
window isn't going to cut it.  My ideal solution would be to create a
split that spans both the blame buffer and the original file, but I
don't think there's a practical way to do that, so I've instead settled
for using :topleft/:botright instead, as appropriate.  The other natural
solution would be to switch to the original file and split there, but
that means we'd end up with a scroll-bound window with a mismatched
height, which behaves exactly as poorly as you would expect.

Furthermore, I've made the decision to extend this behavior to paginated
output windows (e.g., `:Git log`), but *not* to other window creation
commands like :Gsplit.

References: https://github.com/tpope/vim-fugitive/issues/2035
---
 autoload/fugitive.vim | 24 +++++++++++++++++++-----
 1 file changed, 19 insertions(+), 5 deletions(-)

diff --git a/autoload/fugitive.vim b/autoload/fugitive.vim
index b03a8a0..bb4886e 100644
--- a/autoload/fugitive.vim
+++ b/autoload/fugitive.vim
@@ -142,14 +142,22 @@ function! s:Mods(mods, ...) abort
   let mods = substitute(a:mods, '\C<mods>', '', '')
   let mods = mods =~# '\S$' ? mods . ' ' : mods
   if a:0 && mods !~# '\<\%(aboveleft\|belowright\|leftabove\|rightbelow\|topleft\|botright\|tab\)\>'
-    if a:1 ==# 'Edge'
+    let default = a:1
+    if default ==# 'SpanOrigin'
+      if s:OriginBufnr() > 0 && (mods =~# '\<vertical\>' ? &winfixheight : &winfixwidth)
+        let default = 'Edge'
+      else
+        let default = ''
+      endif
+    endif
+    if default ==# 'Edge'
       if mods =~# '\<vertical\>' ? &splitright : &splitbelow
         let mods = 'botright ' . mods
       else
         let mods = 'topleft ' . mods
       endif
     else
-      let mods = a:1 . ' ' . mods
+      let mods = default . ' ' . mods
     endif
   endif
   return substitute(mods, '\s\+', ' ', 'g')
@@ -3294,6 +3302,11 @@ function! s:TempDelete(file) abort
   return ''
 endfunction
 
+function! s:OriginBufnr(...) abort
+  let state = s:TempState(a:0 ? a:1 : bufnr(''))
+  return get(state, 'origin_bufnr', -1)
+endfunction
+
 augroup fugitive_temp
   autocmd!
   autocmd BufReadPre  * exe s:TempReadPre( +expand('<abuf>'))
@@ -3346,7 +3359,8 @@ function! s:RunEdit(state, tmp, job) abort
       let noequalalways = 1
       setglobal equalalways
     endif
-    exe substitute(a:state.mods, '\<tab\>', '-tab', 'g') 'keepalt split' s:fnameescape(file)
+    let mods = s:Mods(a:state.mods, 'SpanOrigin')
+    exe substitute(mods, '\<tab\>', '-tab', 'g') 'keepalt split' s:fnameescape(file)
   finally
     if exists('l:noequalalways')
       setglobal noequalalways
@@ -3807,9 +3821,9 @@ function! fugitive#Command(line1, line2, range, bang, mods, arg, ...) abort
     if pager is# 2 && a:bang && a:line2 >= 0
       let [do_edit, after_edit] = s:ReadPrepare(a:line1, a:line2, a:range, a:mods)
     elseif pager is# 2 && a:bang
-      let do_edit = s:Mods(a:mods) . 'pedit'
+      let do_edit = s:Mods(a:mods, 'SpanOrigin') . 'pedit'
     elseif !curwin
-      let do_edit = s:Mods(a:mods) . 'split'
+      let do_edit = s:Mods(a:mods, 'SpanOrigin') . 'split'
     else
       let do_edit = s:Mods(a:mods) . 'edit'
       call s:BlurStatus()