git: Add revert to special action contexts

revert is very similar to cherry-pick and has a sequence variant.

modules/git/README.md

@@ -389,6 +389,8 @@ The following contexts must be enabled with the following zstyle:
 | rebase               |    value    | Rebasing
 | rebase-interactive   |    value    | Rebasing interactively
 | rebase-merge         |    value    | Rebasing merge
+| revert               |    value    | Reverting
+| revert-sequence      |    value    | Reverting sequence
 
 First, format the repository state attributes. For example, to format the branch
 and remote names, define the following styles.

modules/git/functions/git-info

@@ -5,7 +5,7 @@
 #   Sorin Ionescu <sorin.ionescu@gmail.com>
 #
 
-# Gets the Git special action (am, bisect, cherry, merge, rebase).
+# Gets the Git special action (am, bisect, cherry, merge, rebase, revert).
 # Borrowed from vcs_info and edited.
 function _git-action {
   local action_dir
@@ -18,6 +18,8 @@ function _git-action {
   local rebase_formatted
   local rebase_interactive_formatted
   local rebase_merge_formatted
+  local revert_formatted
+  local revert_sequence_formatted
 
   for action_dir in \
     "${git_dir}/rebase-apply" \
@@ -80,6 +82,18 @@ function _git-action {
     return 0
   fi
 
+  if [[ -f "${git_dir}/REVERT_HEAD" ]]; then
+    if [[ -d "${git_dir}/sequencer" ]] ; then
+      zstyle -s ':prezto:module:git:info:action:revert-sequence' format 'revert_sequence_formatted' || revert_sequence_formatted='revert-sequence'
+      print "$revert_sequence_formatted"
+    else
+      zstyle -s ':prezto:module:git:info:action:revert' format 'revert_formatted' || revert_formatted='revert'
+      print "$revert_formatted"
+    fi
+
+    return 0
+  fi
+
   if [[ -f "${git_dir}/BISECT_LOG" ]]; then
     zstyle -s ':prezto:module:git:info:action:bisect' format 'bisect_formatted' || bisect_formatted='bisect'
     print "$bisect_formatted"