Resolve name to oid in argparse

how_to/Change_23.md

@@ -0,0 +1,22 @@
+- tag: Resolve name to oid in argparse
+
+It's nice that we can create tags, but now let's actually make them usable from
+the CLI.
+
+In *base.py*, we'll create `get_oid` to resolve a "name" to an OID. A name can
+either be a ref (in which case `get_oid` will return the OID that the ref points
+to) or an OID (in which case `get_oid` will just return that same OID).
+
+Next, we'll modify the argument parser in *cli.py* to call `get_oid` on all
+arguments which are expected to be an OID. This way we can pass a ref there
+instead of an OID.
+
+At this point we can do something like:
+```
+$ ugit tag mytag d8d43b0e3a21df0c845e185d08be8e4028787069
+$ ugit log refs/tags/mytag
+# Will print log of commits starting at d8d43b0e...
+$ ugit checkout refs/tags/mytag
+# Will checkout commit d8d43b0e...
+etc...
+```

ugit/base.py

@@ -96,9 +96,11 @@ def commit(message):
 
     return oid
 
+
 def create_tag(name, oid):
     data.update_ref(f"refs/tags/{name}", oid)
 
+
 def checkout(oid):
     commit = get_commit(oid)
     read_tree(commit.tree)
@@ -126,5 +128,9 @@ def get_commit(oid):
     return Commit(tree=tree, parent=parent, message=message)
 
 
+def get_oid(name):
+    return data.get_ref(name) or name
+
+
 def is_ignored(path):
     return ".ugit" in path.split("/")

ugit/cli.py

@@ -19,6 +19,8 @@ def parse_args():
     commands = parser.add_subparsers(dest="command")
     commands.required = True
 
+    oid = base.get_oid
+
     init_parser = commands.add_parser("init")
     init_parser.set_defaults(func=init)
 
@@ -28,14 +30,14 @@ def parse_args():
 
     cat_file_parser = commands.add_parser("cat-file")
     cat_file_parser.set_defaults(func=cat_file)
-    cat_file_parser.add_argument("object")
+    cat_file_parser.add_argument("object", type=oid)
 
     write_tree_parser = commands.add_parser("write-tree")
     write_tree_parser.set_defaults(func=write_tree)
 
     read_tree_parser = commands.add_parser("read-tree")
     read_tree_parser.set_defaults(func=read_tree)
-    read_tree_parser.add_argument("tree")
+    read_tree_parser.add_argument("tree", type=oid)
 
     commit_parser = commands.add_parser("commit")
     commit_parser.set_defaults(func=commit)
@@ -43,16 +45,16 @@ def parse_args():
 
     log_parser = commands.add_parser("log")
     log_parser.set_defaults(func=log)
-    log_parser.add_argument("oid", nargs="?")
+    log_parser.add_argument("oid", type=oid, nargs="?")
 
     checkout_parser = commands.add_parser("checkout")
     checkout_parser.set_defaults(func=checkout)
-    checkout_parser.add_argument("oid")
+    checkout_parser.add_argument("oid", type=oid)
 
     tag_parser = commands.add_parser("tag")
     tag_parser.set_defaults(func=tag)
     tag_parser.add_argument("name")
-    tag_parser.add_argument("oid", nargs="?")
+    tag_parser.add_argument("oid", type=oid, nargs="?")
 
     return parser.parse_args()