Display unambiguous sign when hunks overlap.

See #556.

autoload/gitgutter/highlight.vim

@@ -73,6 +73,7 @@ function! gitgutter#highlight#define_signs() abort
   sign define GitGutterLineModified
   sign define GitGutterLineRemoved
   sign define GitGutterLineRemovedFirstLine
+  sign define GitGutterLineRemovedAboveAndBelow
   sign define GitGutterLineModifiedRemoved
   sign define GitGutterDummy
 
@@ -86,6 +87,7 @@ function! s:define_sign_text() abort
   execute "sign define GitGutterLineModified         text=" . g:gitgutter_sign_modified
   execute "sign define GitGutterLineRemoved          text=" . g:gitgutter_sign_removed
   execute "sign define GitGutterLineRemovedFirstLine text=" . g:gitgutter_sign_removed_first_line
+  execute "sign define GitGutterLineRemovedAboveAndBelow  text=" . g:gitgutter_sign_removed_above_and_below
   execute "sign define GitGutterLineModifiedRemoved  text=" . g:gitgutter_sign_modified_removed
 endfunction
 
@@ -99,12 +101,14 @@ function! gitgutter#highlight#define_sign_text_highlights() abort
     sign define GitGutterLineModified         texthl=GitGutterChange
     sign define GitGutterLineRemoved          texthl=GitGutterDelete
     sign define GitGutterLineRemovedFirstLine texthl=GitGutterDelete
+    sign define GitGutterLineRemovedAboveAndBelow  texthl=GitGutterDelete
     sign define GitGutterLineModifiedRemoved  texthl=GitGutterChangeDelete
   else
     sign define GitGutterLineAdded            texthl=GitGutterAddInvisible
     sign define GitGutterLineModified         texthl=GitGutterChangeInvisible
     sign define GitGutterLineRemoved          texthl=GitGutterDeleteInvisible
     sign define GitGutterLineRemovedFirstLine texthl=GitGutterDeleteInvisible
+    sign define GitGutterLineRemovedAboveAndBelow  texthl=GitGutterDeleteInvisible
     sign define GitGutterLineModifiedRemoved  texthl=GitGutterChangeDeleteInvisible
   endif
 endfunction
@@ -115,12 +119,14 @@ function! s:define_sign_line_highlights() abort
     sign define GitGutterLineModified         linehl=GitGutterChangeLine
     sign define GitGutterLineRemoved          linehl=GitGutterDeleteLine
     sign define GitGutterLineRemovedFirstLine linehl=GitGutterDeleteLine
+    sign define GitGutterLineRemovedAboveAndBelow  linehl=GitGutterDeleteLine
     sign define GitGutterLineModifiedRemoved  linehl=GitGutterChangeDeleteLine
   else
     sign define GitGutterLineAdded            linehl=
     sign define GitGutterLineModified         linehl=
     sign define GitGutterLineRemoved          linehl=
     sign define GitGutterLineRemovedFirstLine linehl=
+    sign define GitGutterLineRemovedAboveAndBelow  linehl=
     sign define GitGutterLineModifiedRemoved  linehl=
   endif
 endfunction

autoload/gitgutter/hunk.vim

@@ -93,6 +93,9 @@ function! s:current_hunk() abort
   return current_hunk
 endfunction
 
+" A line can be in 0 or 1 hunks, with the following exception: when the first
+" line(s) of a file has been deleted, and the new second line (and
+" optionally below) has been deleted, the new first line is in two hunks.
 function! gitgutter#hunk#cursor_in_hunk(hunk) abort
   let current_line = line('.')
 

autoload/gitgutter/sign.vim

@@ -170,7 +170,16 @@ function! s:upsert_new_gitgutter_signs(bufnr, modified_lines) abort
   let other_signs         = gitgutter#utility#getbufvar(a:bufnr, 'other_signs')
   let old_gitgutter_signs = gitgutter#utility#getbufvar(a:bufnr, 'gitgutter_signs')
 
-  for line in a:modified_lines
+  " Handle special case where the first line is the site of two hunks:
+  " lines deleted above at the start of the file, and lines deleted below from
+  " the (new) second line down.
+  if a:modified_lines[0:1] == [[1, 'removed_first_line'], [1, 'removed']]
+    let modified_lines = [[1, 'removed_above_and_below'] + a:modified_lines[2:]]
+  else
+    let modified_lines = a:modified_lines
+  endif
+
+  for line in modified_lines
     let line_number = line[0]  " <number>
     if index(other_signs, line_number) == -1  " don't clobber others' signs
       let name = s:highlight_name_for_change(line[1])
@@ -213,6 +222,8 @@ function! s:highlight_name_for_change(text) abort
     return 'GitGutterLineModified'
   elseif a:text ==# 'modified_removed'
     return 'GitGutterLineModifiedRemoved'
+  elseif a:text ==# 'removed_above_and_below'
+    return 'GitGutterLineRemovedAboveAndBelow'
   endif
 endfunction