git-shortlog: add page (tldr-pages#2044)

pages/common/git-shortlog.md

@@ -0,0 +1,19 @@
+# git shortlog
+
+> Summarizes the `git log` output.
+
+- View a summary of all the commits made, grouped alphabetically by author name:
+
+`git shortlog`
+
+- View a summary of all the commits made, sorted by the number of commits made:
+
+`git shortlog -n`
+
+- View a summary of all the commits made, grouped by the commiter identities (name and email):
+
+`git shortlog -c`
+
+- View a summary of the last 5 commits (i.e. specify a revision range):
+
+`git shortlog HEAD~{{5}}..HEAD`