Question

In libgit2, how to resolve short ref name to get the full ref name or hash?
What libgit2 function need to be called?

Answer 1

libgit2 supports the full extended SHA-1 syntax through the use of the git_revparse_single() function. In order to retrieve the hash, just pass the retrieved object to the git_object_id()function.

Leveraging git_revparse_single() will allow one to replicate following standard git command line usages:

$ git show master
$ git show heads/master
$ git show e90810b
...

Libgit2 code:

git_repository* repo;
git_object *object;
int error;

... open existing repository ...

/* Short named references
 * Note: Might be considered ambiguous if tags/master
 * and heads/master both exist
 */
error = git_revparse_single(&obj, repo, "master"); 
git_object_free(obj);

/* Less ambiguous name */
error = git_revparse_single(&obj, repo, "heads/master");
git_object_free(obj);

/* Short hash as well */
error = git_revparse_single(&obj, repo, "e90810b"); 
git_object_free(obj);

/* Complex specs */
error = git_revparse_single(&obj, repo, "master@{0}~1^1"); 
git_object_free(obj);

/* Tree entries */
error = git_revparse_single(&obj, repo, "test/master@{1}:branch_file.txt"); 
git_object_free(obj);

For more information or examples about usage, you can peek at the unit tests.

Note: There’s currently no built-in exposed way to retrieve a canonical reference name from a short reference name.

Update

The amazing @CarlosMartinNieto made it happen.

Libgit2 now exposes git_reference_dwim which retrieves a reference by its short name (e.g. master, heads/master, …)

• Header
• Libgit 2 commit introducing this change