git: Add basic git rebase quick-alias

Every so often, when doing rebases, you need quick access to the git
rebase command to do something like '--edit-todo' or similar.

Every time, I tried to do `grb` since I already use these quick
shortcuts for `grbm` rebasing onto master, and `grbi`, `grbc` to rebase
interactively or continue one in progress. The base version is thus a
natural extension of the more detailed implementations of rebasing.

git/.config/sh/alias.d/git.sh

@@ -52,6 +52,7 @@ alias grv='git remote -v'
 alias grs='git restore --staged'
 alias grs!='git restore'
 
+alias grb='git rebase'
 alias grbi='git rebase -i'
 alias grbc='git rebase --continue'
 alias grbm='git rebase master'