Add another shadow to the git aliases

Originally submitted in https://github.com/sorin-ionescu/prezto/pull/979

modules/git/README.md

@@ -312,9 +312,10 @@ zstyle ':prezto:module:git:alias' skip 'yes'
 
 The following aliases may shadow system commands:
 
-  - `gpt` shadows the [GUID partition table maintenance utility][4].
-  - `gs` shadows the [Ghostscript][5].
   - `gb` shadows the [GB][9].
+  - `gm` shadows the [Graphics Magick image processor][11].
+  - `gpt` shadows the [GUID partition table maintenance utility][4].
+  - `gs` shadows the [Ghostscript interpreter and previewer][5].
 
 If you frequently use the above commands, you may wish to remove said aliases
 from this module or to disable them at the bottom of the zshrc with `unalias`.
@@ -439,9 +440,10 @@ Authors
 [2]: https://github.com/defunkt/hub
 [3]: https://www.github.com
 [4]: http://www.manpagez.com/man/8/gpt/
-[5]: http://linux.die.net/man/1/gs
+[5]: http://www.manpagez.com/man/1/gs/
 [6]: https://github.com/sorin-ionescu/prezto/issues
 [7]: https://github.com/sorin-ionescu/prezto/issues/219
 [8]: http://www.kernel.org/pub/software/scm/git/docs/git-log.html
 [9]: https://getgb.io/
 [10]: https://github.com/blog/985-git-io-github-url-shortener
+[11]: http://www.manpagez.com/man/1/gm/