fetch: remove `unshallow` option

The `depth` field is suitable to specify unshallowing; provide an enum
to aide in specifying the `unshallow` value.

include/git2/remote.h

@@ -702,6 +702,15 @@ typedef enum {
 	GIT_REMOTE_DOWNLOAD_TAGS_ALL
 } git_remote_autotag_option_t;
 
+/** Constants for fetch depth (shallowness of fetch). */
+typedef enum {
+	/** The fetch is "full" (not shallow). This is the default. */
+	GIT_FETCH_DEPTH_FULL = 0,
+
+	/** The fetch should "unshallow" and fetch missing data. */
+	GIT_FETCH_DEPTH_UNSHALLOW = 2147483647
+} git_fetch_depth_t;
+
 /**
  * Fetch options structure.
  *
@@ -744,20 +753,15 @@ typedef struct {
 	git_proxy_options proxy_opts;
 
 	/**
-	 * Depth of the fetch to perform, or 0 for full history.
+	 * Depth of the fetch to perform, or `GIT_FETCH_DEPTH_FULL`
+	 * (or `0`) for full history, or `GIT_FETCH_DEPTH_UNSHALLOW`
+	 * to "unshallow" a shallow repository.
 	 *
-	 * The default is 0.
+	 * The default is full (`GIT_FETCH_DEPTH_FULL` or `0`).
 	 */
 	int depth;
 
 	/**
-	 * Convert a shallow repository to a full repository.
-	 *
-	 * The default is 0, which means the flag is off.
-	 */
-	int unshallow;
-
-	/**
 	 * Whether to allow off-site redirects.  If this is not
 	 * specified, the `http.followRedirects` configuration setting
 	 * will be consulted.

src/libgit2/fetch.c

@@ -174,10 +174,8 @@ int git_fetch_negotiate(git_remote *remote, const git_fetch_options *opts)
 	remote->need_pack = 0;
 
 	if (opts) {
-		GIT_ASSERT_ARG(opts->unshallow == 0 || opts->depth == 0);
 		GIT_ASSERT_ARG(opts->depth >= 0);
-
-		remote->nego.depth = opts->unshallow ? INT_MAX : opts->depth;
+		remote->nego.depth = opts->depth;
 	}
 
 	if (filter_wants(remote, opts) < 0)

tests/libgit2/online/shallow.c

@@ -143,7 +143,7 @@ void test_online_shallow__unshallow(void)
 	cl_git_pass(git_clone(&repo, "https://github.com/libgit2/TestGitRepository", git_str_cstr(&path), &clone_opts));
 	cl_assert_equal_b(true, git_repository_is_shallow(repo));
 
-	fetch_opts.unshallow = 1;
+	fetch_opts.depth = GIT_FETCH_DEPTH_UNSHALLOW;
 	cl_git_pass(git_remote_lookup(&origin, repo, "origin"));
 
 	cl_git_pass(git_remote_fetch(origin, NULL, &fetch_opts, NULL));