[git] Make gpf alias safer

Fixes #303. Closes #304.

As a reference,
https://github.com/k88hudson/git-flight-rules/blob/master/README.md#i-want-to-delete-or-remove-my-last-commit
also recommends using --force-with-lease.

modules/git/README.md

@@ -118,7 +118,8 @@ Aliases
 ### Push
 
   * `gp` updates remote refs along with associated objects.
-  * `gpf` forces a push.
+  * `gpf` forces a push safely (with "lease").
+  * `gpF` forces a push.
   * `gpa` pushes all branches.
   * `gpA` pushes all branches and tags.
   * `gpt` pushes all tags.

modules/git/init.zsh

@@ -111,7 +111,8 @@ alias gmt='git mergetool'
 
 # Push (p)
 alias gp='git push'
-alias gpf='git push --force'
+alias gpf='git push --force-with-lease'
+alias gpF='git push --force'
 alias gpa='git push --all'
 alias gpA='git push --all && git push --tags'
 alias gpt='git push --tags'