Merge branch 'perforce-support'

Closes #46.

README.md

@@ -10,7 +10,8 @@ It's __fast__, __highly configurable__ and __well documented__.
 
 Features:
 
-- supports git, mercurial, darcs, bazaar, subversion, cvs, rcs, fossil
+- supports git, mercurial, darcs, bazaar, subversion, cvs, rcs, fossil, accurev,
+  perforce
 - quick jumping between blocks of changed lines
 - apart from signs there is also optional line highlighting
 - fully configurable through global variables (options and mappings)
@@ -102,6 +103,7 @@ Currently the following VCS are supported:
 - rcs
 - fossil
 - accurev
+- perforce
 
 #### quick jumping between changed lines
 

autoload/sy/repo.vim

@@ -26,7 +26,7 @@ endif
 
 " Function: #detect {{{1
 function! sy#repo#detect(path) abort
-  for type in get(g:, 'signify_vcs_list', [ 'git', 'hg', 'svn', 'darcs', 'bzr', 'fossil', 'cvs', 'rcs', 'accurev' ])
+  for type in get(g:, 'signify_vcs_list', [ 'git', 'hg', 'svn', 'darcs', 'bzr', 'fossil', 'cvs', 'rcs', 'accurev', 'perforce' ])
     let diff = sy#repo#get_diff_{type}(a:path)
     if !empty(diff)
       return [ diff, type ]
@@ -139,6 +139,14 @@ function! sy#repo#get_diff_accurev(path) abort
   endif
 endfunction
 
+" Function: #get_diff_perforce {{{1
+function! sy#repo#get_diff_perforce(path) abort
+  if executable('perforce')
+    let diff = system('env P4DIFF=diff p4 diff -dU0 -- '. sy#util#escape(a:path))
+    return v:shell_error ? '' : diff
+  endif
+endfunction
+
 " Function: #process_diff {{{1
 function! sy#repo#process_diff(path, diff) abort
   " Determine where we have to put our signs.

doc/signify.txt

@@ -93,7 +93,8 @@ default values, as long as no "Default:" section is given.
 
     let g:signify_vcs_list = [ 'git', 'hg' ]
 
-Default: ['git', 'hg', 'svn', 'darcs', 'bzr', 'fossil', 'cvs', 'rcs', 'accurev']
+Default: ['git', 'hg', 'svn', 'darcs', 'bzr', 'fossil', 'cvs', 'rcs',
+'accurev', 'perforce']
 
 This variable determines the VCS to check for and in what order. If you only
 use git and mercurial, you can shorten the list to the shown example. If you