git: Some improvements to git configuration

Use fast forward only for merge, auto stash when doing rebase and take
care of tags when doing a push.

git/.gitconfig

@@ -19,16 +19,21 @@
 [merge]
 	tool = vimdiff3
 	conflictstyle = diff3
+	ff = only
 [mergetool]
 	prompt = false
 [mergetool "vimdiff"]
 	cmd = nvim -d $BASE $LOCAL $REMOTE $MERGED -c '$wincmd w' -c 'wincmd J'
 	trustExitCode = true
 	keepBackup = false
+[rebase]
+	autoStash = true
 [commit]
 	verbose = true
 [pull]
 	rebase = false
+[push]
+	followTags = true
 [interactive]
 	diffFilter = delta --color-only
 [delta]