Add support for yadm

Closes https://github.com/mhinz/vim-signify/issues/297

README.md

@@ -8,7 +8,7 @@ removed lines in a file that is managed by a version control system (VCS)._
 ---
 
 - Supports **git**, **mercurial**, **darcs**, **bazaar**, **subversion**,
-  **cvs**, **rcs**, **fossil**, **accurev**, **perforce**, **tfs**.
+  **cvs**, **rcs**, **fossil**, **accurev**, **perforce**, **tfs**, **yadm**.
 - **Asynchronous** execution of VCS tools for Vim 7.4.1967+ and Neovim.
 - **Preserves signs** from other plugins.
 - Handles **nested repositories** controlled by different VCS.

autoload/sy/repo.vim

@@ -145,6 +145,13 @@ function! sy#repo#get_diff_git(sy, exitval, diff) abort
   call s:get_diff_end(a:sy, found_diff, 'git', diff)
 endfunction
 
+" Function: #get_diff_yadm {{{1
+function! sy#repo#get_diff_yadm(sy, exitval, diff) abort
+  call sy#verbose('get_diff_yadm()', 'yadm')
+  let [found_diff, diff] = a:exitval ? [0, []] : [1, a:diff]
+  call s:get_diff_end(a:sy, found_diff, 'yadm', diff)
+endfunction
+
 " Function: #get_diff_hg {{{1
 function! sy#repo#get_diff_hg(sy, exitval, diff) abort
   call sy#verbose('get_diff_hg()', 'hg')
@@ -322,7 +329,7 @@ endfunction
 
 " Function: s:get_vcs_path {{{1
 function! s:get_vcs_path(vcs) abort
-  return (a:vcs =~# '\v(git|cvs|accurev|tfs)') ? b:sy.info.file : b:sy.info.path
+  return (a:vcs =~# '\v(git|cvs|accurev|tfs|yadm)') ? b:sy.info.file : b:sy.info.path
 endfunction
 
 " Function: s:expand_cmd {{{1
@@ -442,6 +449,7 @@ let s:difftool = get(g:, 'signify_difftool', 'diff')
 if executable(s:difftool)
   let s:vcs_dict = {
         \ 'git':      'git',
+        \ 'yadm':     'yadm',
         \ 'hg':       'hg',
         \ 'svn':      'svn',
         \ 'darcs':    'darcs',
@@ -457,6 +465,7 @@ else
   call sy#verbose('No "diff" executable found. Disable support for svn, darcs, bzr.')
   let s:vcs_dict = {
         \ 'git':      'git',
+        \ 'yadm':     'yadm',
         \ 'hg':       'hg',
         \ 'fossil':   'fossil',
         \ 'cvs':      'cvs',
@@ -474,6 +483,7 @@ endif
 
 let s:default_vcs_cmds = {
       \ 'git':      'git diff --no-color --no-ext-diff -U0 -- %f',
+      \ 'yadm':     'yadm diff --no-color --no-ext-diff -U0 -- %f',
       \ 'hg':       'hg diff --color=never --config aliases.diff= --nodates -U0 -- %f',
       \ 'svn':      'svn diff --diff-cmd %d -x -U0 -- %f',
       \ 'bzr':      'bzr diff --using %d --diff-options=-U0 -- %f',
@@ -488,6 +498,7 @@ let s:default_vcs_cmds = {
 
 let s:default_vcs_cmds_diffmode = {
       \ 'git':      'git show HEAD:./%f',
+      \ 'yadm':     'yadm show HEAD:./%f',
       \ 'hg':       'hg cat %f',
       \ 'svn':      'svn cat %f',
       \ 'bzr':      'bzr cat %f',

doc/signify.txt

@@ -47,6 +47,7 @@ Supported VCS:~
     accurev
     perforce
     tfs
+    yadm
 <
 ==============================================================================
 MODUS OPERANDI                                          *signify-modus-operandi*
@@ -83,7 +84,7 @@ If signs aren't showing up as expected, see if |signify-:SignifyDebug| shows
 anything suspicious. It will try all VCS and shows either errors or a diff for
 each VCS.
 
-If the output looks fine though, create an issue on Github:
+If the output looks fine though, create an issue on GitHub:
 
     https://github.com/mhinz/vim-signify/issues/new
 
@@ -165,6 +166,7 @@ Possible values: 'accurev'
                  'rcs'
                  'svn'
                  'tfs'
+                 'yadm'
 
 NOTE: This is the most important option, so read closely.
 
@@ -251,6 +253,7 @@ Default:
 >
     let g:signify_vcs_cmds = {
       \ 'git':      'git diff --no-color --no-ext-diff -U0 -- %f',
+      \ 'yadm':     'yadm diff --no-color --no-ext-diff -U0 -- %f',
       \ 'hg':       'hg diff --config extensions.color=! --config defaults.diff= --nodates -U0 -- %f',
       \ 'svn':      'svn diff --diff-cmd %d -x -U0 -- %f',
       \ 'bzr':      'bzr diff --using %d --diff-options=-U0 -- %f',
@@ -267,6 +270,7 @@ Default:
                                                    *g:signify_vcs_cmds_diffmode*  >
     let g:signify_vcs_cmds_diffmode = {
       \ 'git':      'git show HEAD:./%f',
+      \ 'yadm':     'yadm show HEAD:./%f',
       \ 'hg':       'hg cat %f',
       \ 'svn':      'svn cat %f',
       \ 'bzr':      'bzr cat %f',