support display only tail end of a branch; as well as custom format

functions. resolves #710.

autoload/airline/extensions/branch.vim

@@ -9,6 +9,21 @@ if !s:has_fugitive && !s:has_lawrencium && !s:has_vcscommand
   finish
 endif
 
+let s:head_format = get(g:, 'airline#extensions#branch#format', 0)
+if s:head_format == 1
+  function! s:format_name(name)
+    return fnamemodify(a:name, ':t')
+  endfunction
+elseif type(s:head_format) == type('')
+  function! s:format_name(name)
+    return call(s:head_format, [a:name])
+  endfunction
+else
+  function! s:format_name(name)
+    return a:name
+  endfunction
+endif
+
 let s:git_dirs = {}
 function! s:get_git_branch(path)
   if has_key(s:git_dirs, a:path)
@@ -79,6 +94,7 @@ function! airline#extensions#branch#head()
     endif
   endif
 
+  let b:airline_head = s:format_name(b:airline_head)
   return b:airline_head
 endfunction
 

doc/airline.txt

@@ -296,13 +296,27 @@ vcscommand   <http://www.vim.org/scripts/script.php?script_id=90>
 <
 * change the text for when no branch is detected >
   let g:airline#extensions#branch#empty_message = ''
-
+<
 * use vcscommand.vim if available >
   let g:airline#extensions#branch#use_vcscommand = 0
-
+<
 * truncate long branch names to a fixed length >
   let g:airline#extensions#branch#displayed_head_limit = 10
+<
+* customize formatting of branch name >
+  " default value leaves the name unmodifed
+  let g:airline#extensions#branch#format = 0
 
+  " to only show the tail, e.g. a branch 'feature/foo' show 'foo'
+  let g:airline#extensions#branch#format = 1
+
+  " if a string is provided, it should be the name of a function that
+  " takes a string and returns the desired value
+  let g:airline#extensions#branch#format = 'CustomBranchName'
+  function! CustomBranchName(name)
+    return '[' . a:name . ']'
+  endfunction
+<
 -------------------------------------                    *airline-syntastic*
 syntastic <https://github.com/scrooloose/syntastic>