git-cat-file: add page (#4492)

pages/common/git-cat-file.md

@@ -0,0 +1,16 @@
+# git cat-file
+
+> Provide content or type and size information for git repository objects.
+> More information: <https://git-scm.com/docs/git-cat-file>.
+
+- Get the [s]ize of the HEAD commit in bytes:
+
+`git cat-file -s HEAD`
+
+- Get the [t]ype (blob, tree, commit, tag) of a given git object:
+
+`git cat-file -t {{8c442dc3}}`
+
+- Pretty-[p]rint the contents of a given git object based on its type:
+
+`git cat-file -p {{HEAD~2}}`