[PATCH v2 4/6] fetch: add --bundle-uri option

["Derrick Stolee via GitGitGadget" <gitgitgadget@gmail.com>]

From: Derrick Stolee <derrickstolee@github.com>

Teach 'git fetch' a new --bundle-uri=<uri> option which changes the mode
from fetching from a remote using the Git protocol to fetching a bundle
from the given <uri>. See Documentation/technical/bundle-uri.txt for
more information on the design of this feature.

This implementation is limited to the most basic version of the feature.
We expect the content at that URI to be a bundle file, not a bundle
list. Bundle lists will be implemented later.

This implementation is sufficient for a bundle provider to create a
single bootstrap bundle for a large repository. The user would bootstrap
a repository using a sequence of Git commands, such as:

 1. git init <repo> && cd <repo>
 2. git fetch --bundle-uri=<uri>
 3. git remote add origin <url>
 4. git fetch origin
 5. git checkout FETCH_HEAD

Since the unbundle_from_file() in bundle-uri.c stores the bundled refs
into the refs/bundle/* namespace, those references are useful for the
fetch negotiation in step 4, reducing the size of the download in that
step.

Later changes will make this seamless within a 'git clone' command, but
this implementation is large enough to delay that integration.

Currently, this option supports local filenames. Other protocols will be
added in the future.

Signed-off-by: Derrick Stolee <derrickstolee@github.com>
---
 Documentation/fetch-options.txt |  5 +++++
 Documentation/git-fetch.txt     |  1 +
 builtin/fetch.c                 | 10 ++++++++++
 bundle-uri.c                    |  8 ++++++--
 t/t5558-fetch-bundle-uri.sh     | 34 +++++++++++++++++++++++++++++++++
 5 files changed, 56 insertions(+), 2 deletions(-)
 create mode 100755 t/t5558-fetch-bundle-uri.sh

diff --git a/Documentation/fetch-options.txt b/Documentation/fetch-options.txt
index 622bd84768b..09bd1feeed8 100644
--- a/Documentation/fetch-options.txt
+++ b/Documentation/fetch-options.txt
@@ -317,3 +317,8 @@ endif::git-pull[]
 -6::
 --ipv6::
 	Use IPv6 addresses only, ignoring IPv4 addresses.
+
+--bundle-uri=<uri>::
+	Instead of fetching from a remote, fetch a bundle from the given
+	`<uri>` and unbundle the data into the local repository. The refs
+	in the bundle will be stored under the `refs/bundle/*` namespace.
diff --git a/Documentation/git-fetch.txt b/Documentation/git-fetch.txt
index e9d364669af..4fd8911b336 100644
--- a/Documentation/git-fetch.txt
+++ b/Documentation/git-fetch.txt
@@ -13,6 +13,7 @@ SYNOPSIS
 'git fetch' [<options>] <group>
 'git fetch' --multiple [<options>] [(<repository> | <group>)...]
 'git fetch' --all [<options>]
+'git fetch' --bundle-uri=<uri> [<options>]
 
 
 DESCRIPTION
diff --git a/builtin/fetch.c b/builtin/fetch.c
index e3791f09ed5..cb0d2fbe82c 100644
--- a/builtin/fetch.c
+++ b/builtin/fetch.c
@@ -29,6 +29,7 @@
 #include "commit-graph.h"
 #include "shallow.h"
 #include "worktree.h"
+#include "bundle-uri.h"
 
 #define FORCED_UPDATES_DELAY_WARNING_IN_MS (10 * 1000)
 
@@ -37,6 +38,7 @@ static const char * const builtin_fetch_usage[] = {
 	N_("git fetch [<options>] <group>"),
 	N_("git fetch --multiple [<options>] [(<repository> | <group>)...]"),
 	N_("git fetch --all [<options>]"),
+	N_("git fetch --bundle-uri=<uri> [<options>]"),
 	NULL
 };
 
@@ -86,6 +88,7 @@ static struct string_list negotiation_tip = STRING_LIST_INIT_NODUP;
 static int fetch_write_commit_graph = -1;
 static int stdin_refspecs = 0;
 static int negotiate_only;
+static const char *bundle_uri;
 
 static int git_fetch_config(const char *k, const char *v, void *cb)
 {
@@ -224,6 +227,8 @@ static struct option builtin_fetch_options[] = {
 		 N_("write the commit-graph after fetching")),
 	OPT_BOOL(0, "stdin", &stdin_refspecs,
 		 N_("accept refspecs from stdin")),
+	OPT_STRING(0, "bundle-uri", &bundle_uri, N_("uri"),
+		   N_("download bundle data from the given URI instead of from a remote")),
 	OPT_END()
 };
 
@@ -2181,6 +2186,11 @@ int cmd_fetch(int argc, const char **argv, const char *prefix)
 	if (dry_run)
 		write_fetch_head = 0;
 
+	if (bundle_uri) {
+		result = fetch_bundle_uri(the_repository, bundle_uri);
+		goto cleanup;
+	}
+
 	if (all) {
 		if (argc == 1)
 			die(_("fetch --all does not take a repository argument"));
diff --git a/bundle-uri.c b/bundle-uri.c
index f0abbf434c8..f80a3b14103 100644
--- a/bundle-uri.c
+++ b/bundle-uri.c
@@ -77,11 +77,15 @@ int fetch_bundle_uri(struct repository *r, const char *uri)
 	struct strbuf filename = STRBUF_INIT;
 
 	find_temp_filename(&filename);
-	if ((result = copy_uri_to_file(uri, filename.buf)))
+	if ((result = copy_uri_to_file(uri, filename.buf))) {
+		error(_("failed to download bundle from URI '%s'"), uri);
 		goto cleanup;
+	}
 
-	if ((result = !is_bundle(filename.buf, 0)))
+	if ((result = !is_bundle(filename.buf, 0))) {
+		error(_("file at URI '%s' is not a bundle"), uri);
 		goto cleanup;
+	}
 
 	if ((result = unbundle_from_file(r, filename.buf)))
 		goto cleanup;
diff --git a/t/t5558-fetch-bundle-uri.sh b/t/t5558-fetch-bundle-uri.sh
new file mode 100755
index 00000000000..381e56cac20
--- /dev/null
+++ b/t/t5558-fetch-bundle-uri.sh
@@ -0,0 +1,34 @@
+#!/bin/sh
+
+test_description='test fetching bundles with --bundle-uri'
+
+. ./test-lib.sh
+
+test_expect_success 'fail to fetch from non-existent file' '
+	test_must_fail git fetch --bundle-uri="$(pwd)/does-not-exist" 2>err &&
+	grep "failed to download bundle from URI" err
+'
+
+test_expect_success 'fail to fetch from non-bundle file' '
+	echo bogus >bogus &&
+	test_must_fail git fetch --bundle-uri="$(pwd)/bogus" 2>err &&
+	grep "is not a bundle" err
+'
+
+test_expect_success 'create bundle' '
+	git init fetch-from &&
+	git -C fetch-from checkout -b topic &&
+	test_commit -C fetch-from A &&
+	test_commit -C fetch-from B &&
+	git -C fetch-from bundle create B.bundle topic
+'
+
+test_expect_success 'fetch file bundle' '
+	git init fetch-to &&
+	git -C fetch-to fetch --bundle-uri="$(pwd)/fetch-from/B.bundle" &&
+	git -C fetch-to rev-parse refs/bundles/topic >actual &&
+	git -C fetch-from rev-parse topic >expect &&
+	test_cmp expect actual
+'
+
+test_done
-- 
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