Remove feature gitgutter_escape_grep

Reverts feature introduced in 5c23cadf57

In order to use an escaped grep, please replace
`g:gitgutter_escape_grep=1` with:

    let g:gitgutter_grep_command = '\grep --color=never -e'

README.mkd

@@ -179,7 +179,6 @@ You can customise:
 * Line highlights
 * Extra arguments for `git diff`
 * Key mappings
-* Whether or not to escape `grep` (default to no)
 * Whether or not vim-gitgutter is on initially (defaults to on)
 * Whether or not signs are shown (defaults to yes)
 * Whether or not line highlighting is on initially (defaults to off)
@@ -263,14 +262,6 @@ let g:gitgutter_map_keys = 0
 See above for configuring maps for hunk-jumping and staging/reverting.
 
 
-#### Whether or not to escape `grep`
-
-If you have `grep` aliased to something which changes its output, for example `grep --color=auto -H`, you will need to tell vim-gitgutter to use raw grep:
-
-```viml
-let g:gitgutter_escape_grep = 1
-```
-
 #### Use a custom `grep` command
 
 If you use an alternative to grep, you can tell vim-gitgutter to use it here. It only needs to support extended POSIX regex.

autoload/gitgutter/diff.vim

@@ -4,7 +4,7 @@ if exists('g:gitgutter_grep_command')
 else
   let s:grep_available = executable('grep')
   if s:grep_available
-    let s:grep_command = (g:gitgutter_escape_grep ? '\grep' : 'grep')
+    let s:grep_command = 'grep'
     let s:grep_help = gitgutter#utility#system('grep --help')
     if s:grep_help =~# '--color'
       let s:grep_command .= ' --color=never'

doc/gitgutter.txt

@@ -120,7 +120,6 @@ You can customise:
 - Extra arguments for git-diff
 - Key mappings
 - The grep executable used
-- Whether or not to escape grep (defaults to no)
 - Whether or not vim-gitgutter is on initially (defaults to on)
 - Whether or not signs are shown (defaults to yes)
 - Whether or not line highlighting is on initially (defaults to off)
@@ -213,18 +212,13 @@ To change the hunk-staging/reverting/previewing maps (defaults shown):
   nmap <Leader>hp <Plug>GitGutterPreviewHunk
 <
 
-TO ESCAPE GREP
+TO USE A CUSTOM GREP COMMAND
 
 To use a custom invocation for grep, use this:
 >
   let g:gitgutter_grep_command = 'grep --color=never -e'
 <
 
-To avoid any alias you have for grep, use this:
->
-  let g:gitgutter_escape_grep = 1
-<
-
 TO TURN OFF VIM-GITGUTTER BY DEFAULT
 
 Add to your |vimrc|

plugin/gitgutter.vim

@@ -46,7 +46,6 @@ endtry
 
 call s:set('g:gitgutter_sign_modified_removed',    '~_')
 call s:set('g:gitgutter_diff_args',                  '')
-call s:set('g:gitgutter_escape_grep',                 0)
 call s:set('g:gitgutter_map_keys',                    1)
 call s:set('g:gitgutter_avoid_cmd_prompt_on_windows', 1)