On 2022.07.25 20:34, Derrick Stolee via GitGitGadget wrote:
> From: Derrick Stolee <derrickstolee@xxxxxxxxxx>
>
> Before implementing a way to fetch bundles into a repository, create the
> basic logic. Assume that the URI is actually a file path. Future logic
> will make this more careful to other protocols.
>
> For now, we also only succeed if the content at the URI is a bundle
> file, not a bundle list. Bundle lists will be implemented in a future
> change.
>
> Note that the discovery of a temporary filename is slightly racy because
> the odb_mkstemp() relies on the temporary file not existing. With the
> current implementation being limited to file copies, we could replace
> the copy_file() with copy_fd(). The tricky part comes in future changes
> that send the filename to 'git remote-https' and its 'get' capability.
> At that point, we need the file descriptor closed _and_ the file
> unlinked.
Ahh, it looks like this was the point I missed in my previous review.
IIUC, we need the file unlinked because http_get_file() will eventually
call finalize_object_file() to move a tempfile to the final object name,
and that will fail if we have an empty file already in place.
> If we were to keep the file descriptor open for the sake of
> normal file copies, then we would pollute the rest of the code for
> little benefit. This is especially the case because we expect that most
> bundle URI use will be based on HTTPS instead of file copies.
>
> Signed-off-by: Derrick Stolee <derrickstolee@xxxxxxxxxx>
> ---
> Makefile | 1 +
> bundle-uri.c | 104 +++++++++++++++++++++++++++++++++++++++++++++++++++
> bundle-uri.h | 14 +++++++
> 3 files changed, 119 insertions(+)
> create mode 100644 bundle-uri.c
> create mode 100644 bundle-uri.h
>
> diff --git a/Makefile b/Makefile
> index 1624471badc..7d5f48069ea 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -906,6 +906,7 @@ LIB_OBJS += blob.o
> LIB_OBJS += bloom.o
> LIB_OBJS += branch.o
> LIB_OBJS += bulk-checkin.o
> +LIB_OBJS += bundle-uri.o
> LIB_OBJS += bundle.o
> LIB_OBJS += cache-tree.o
> LIB_OBJS += cbtree.o
> diff --git a/bundle-uri.c b/bundle-uri.c
> new file mode 100644
> index 00000000000..b35babc36aa
> --- /dev/null
> +++ b/bundle-uri.c
> @@ -0,0 +1,104 @@
> +#include "cache.h"
> +#include "bundle-uri.h"
> +#include "bundle.h"
> +#include "object-store.h"
> +#include "refs.h"
> +#include "run-command.h"
> +
> +static int find_temp_filename(struct strbuf *name)
> +{
> + int fd;
> + /*
> + * Find a temporary filename that is available. This is briefly
> + * racy, but unlikely to collide.
> + */
> + fd = odb_mkstemp(name, "bundles/tmp_uri_XXXXXX");
> + if (fd < 0) {
> + warning(_("failed to create temporary file"));
> + return -1;
> + }
> +
> + close(fd);
> + unlink(name->buf);
> + return 0;
> +}
> +
> +static int copy_uri_to_file(const char *file, const char *uri)
> +{
> + /* File-based URIs only for now. */
> + return copy_file(file, uri, 0);
> +}
> +
> +static int unbundle_from_file(struct repository *r, const char *file)
> +{
> + int result = 0;
> + int bundle_fd;
> + struct bundle_header header = BUNDLE_HEADER_INIT;
> + struct string_list_item *refname;
> + struct strbuf bundle_ref = STRBUF_INIT;
> + size_t bundle_prefix_len;
> +
> + if ((bundle_fd = read_bundle_header(file, &header)) < 0)
> + return 1;
> +
> + if ((result = unbundle(r, &header, bundle_fd, NULL)))
> + return 1;
> +
> + /*
> + * Convert all refs/heads/ from the bundle into refs/bundles/
> + * in the local repository.
> + */
> + strbuf_addstr(&bundle_ref, "refs/bundles/");
> + bundle_prefix_len = bundle_ref.len;
> +
> + for_each_string_list_item(refname, &header.references) {
> + struct object_id *oid = refname->util;
> + struct object_id old_oid;
> + const char *branch_name;
> + int has_old;
> +
> + if (!skip_prefix(refname->string, "refs/heads/", &branch_name))
> + continue;
> +
> + strbuf_setlen(&bundle_ref, bundle_prefix_len);
> + strbuf_addstr(&bundle_ref, branch_name);
> +
> + has_old = !read_ref(bundle_ref.buf, &old_oid);
> + update_ref("fetched bundle", bundle_ref.buf, oid,
> + has_old ? &old_oid : NULL,
> + REF_SKIP_OID_VERIFICATION,
> + UPDATE_REFS_MSG_ON_ERR);
> + }
> +
> + bundle_header_release(&header);
We still also need to release bundle_ref here, right?
> + return result;
> +}
> +
> +int fetch_bundle_uri(struct repository *r, const char *uri)
> +{
> + int result = 0;
> + struct strbuf filename = STRBUF_INIT;
> +
> + if ((result = find_temp_filename(&filename)))
> + goto cleanup;
> +
> + if ((result = copy_uri_to_file(filename.buf, uri))) {
> + warning(_("failed to download bundle from URI '%s'"), uri);
> + goto cleanup;
> + }
> +
> + if ((result = !is_bundle(filename.buf, 0))) {
> + warning(_("file at URI '%s' is not a bundle"), uri);
> + goto cleanup;
> + }
> +
> + if ((result = unbundle_from_file(r, filename.buf))) {
> + warning(_("failed to unbundle bundle from URI '%s'"), uri);
> + goto cleanup;
> + }
> +
> +cleanup:
> + unlink(filename.buf);
> + strbuf_release(&filename);
> + return result;
> +}
> diff --git a/bundle-uri.h b/bundle-uri.h
> new file mode 100644
> index 00000000000..8a152f1ef14
> --- /dev/null
> +++ b/bundle-uri.h
> @@ -0,0 +1,14 @@
> +#ifndef BUNDLE_URI_H
> +#define BUNDLE_URI_H
> +
> +struct repository;
> +
> +/**
> + * Fetch data from the given 'uri' and unbundle the bundle data found
> + * based on that information.
> + *
> + * Returns non-zero if no bundle information is found at the given 'uri'.
> + */
> +int fetch_bundle_uri(struct repository *r, const char *uri);
> +
> +#endif
> --
> gitgitgadget
>
