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![Jonathan Tan](/assets/img/avatar_default.png)
When cloning, we choose the default branch based on the remote HEAD. But if there is no remote HEAD reported (which could happen if the target of the remote HEAD is unborn), we'll fall back to using our local init.defaultBranch. Traditionally this hasn't been a big deal, because most repos used "master" as the default. But these days it is likely to cause confusion if the server and client implementations choose different values (e.g., if the remote started with "main", we may choose "master" locally, create commits there, and then the user is surprised when they push to "master" and not "main"). To solve this, the remote needs to communicate the target of the HEAD symref, even if it is unborn, and "git clone" needs to use this information. Currently, symrefs that have unborn targets (such as in this case) are not communicated by the protocol. Teach Git to advertise and support the "unborn" feature in "ls-refs" (by default, this is advertised, but server administrators may turn this off through the lsrefs.unborn config). This feature indicates that "ls-refs" supports the "unborn" argument; when it is specified, "ls-refs" will send the HEAD symref with the name of its unborn target. This change is only for protocol v2. A similar change for protocol v0 would require independent protocol design (there being no analogous position to signal support for "unborn") and client-side plumbing of the data required, so the scope of this patch set is limited to protocol v2. The client side will be updated to use this in a subsequent commit. Signed-off-by: Jonathan Tan <jonathantanmy@google.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
307 lines
7.5 KiB
C
307 lines
7.5 KiB
C
#include "cache.h"
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#include "repository.h"
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#include "config.h"
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#include "pkt-line.h"
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#include "version.h"
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#include "strvec.h"
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#include "ls-refs.h"
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#include "serve.h"
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#include "upload-pack.h"
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static int advertise_sid;
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static int always_advertise(struct repository *r,
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struct strbuf *value)
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{
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return 1;
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}
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static int agent_advertise(struct repository *r,
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struct strbuf *value)
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{
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if (value)
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strbuf_addstr(value, git_user_agent_sanitized());
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return 1;
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}
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static int object_format_advertise(struct repository *r,
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struct strbuf *value)
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{
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if (value)
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strbuf_addstr(value, r->hash_algo->name);
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return 1;
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}
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static int session_id_advertise(struct repository *r, struct strbuf *value)
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{
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if (!advertise_sid)
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return 0;
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if (value)
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strbuf_addstr(value, trace2_session_id());
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return 1;
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}
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struct protocol_capability {
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/*
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* The name of the capability. The server uses this name when
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* advertising this capability, and the client uses this name to
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* specify this capability.
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*/
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const char *name;
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/*
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* Function queried to see if a capability should be advertised.
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* Optionally a value can be specified by adding it to 'value'.
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* If a value is added to 'value', the server will advertise this
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* capability as "<name>=<value>" instead of "<name>".
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*/
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int (*advertise)(struct repository *r, struct strbuf *value);
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/*
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* Function called when a client requests the capability as a command.
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* The function will be provided the capabilities requested via 'keys'
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* as well as a struct packet_reader 'request' which the command should
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* use to read the command specific part of the request. Every command
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* MUST read until a flush packet is seen before sending a response.
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*
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* This field should be NULL for capabilities which are not commands.
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*/
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int (*command)(struct repository *r,
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struct strvec *keys,
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struct packet_reader *request);
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};
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static struct protocol_capability capabilities[] = {
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{ "agent", agent_advertise, NULL },
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{ "ls-refs", ls_refs_advertise, ls_refs },
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{ "fetch", upload_pack_advertise, upload_pack_v2 },
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{ "server-option", always_advertise, NULL },
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{ "object-format", object_format_advertise, NULL },
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{ "session-id", session_id_advertise, NULL },
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};
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static void advertise_capabilities(void)
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{
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struct strbuf capability = STRBUF_INIT;
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struct strbuf value = STRBUF_INIT;
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int i;
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for (i = 0; i < ARRAY_SIZE(capabilities); i++) {
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struct protocol_capability *c = &capabilities[i];
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if (c->advertise(the_repository, &value)) {
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strbuf_addstr(&capability, c->name);
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if (value.len) {
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strbuf_addch(&capability, '=');
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strbuf_addbuf(&capability, &value);
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}
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strbuf_addch(&capability, '\n');
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packet_write(1, capability.buf, capability.len);
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}
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strbuf_reset(&capability);
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strbuf_reset(&value);
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}
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packet_flush(1);
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strbuf_release(&capability);
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strbuf_release(&value);
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}
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static struct protocol_capability *get_capability(const char *key)
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{
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int i;
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if (!key)
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return NULL;
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for (i = 0; i < ARRAY_SIZE(capabilities); i++) {
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struct protocol_capability *c = &capabilities[i];
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const char *out;
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if (skip_prefix(key, c->name, &out) && (!*out || *out == '='))
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return c;
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}
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return NULL;
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}
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static int is_valid_capability(const char *key)
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{
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const struct protocol_capability *c = get_capability(key);
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return c && c->advertise(the_repository, NULL);
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}
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static int is_command(const char *key, struct protocol_capability **command)
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{
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const char *out;
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if (skip_prefix(key, "command=", &out)) {
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struct protocol_capability *cmd = get_capability(out);
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if (*command)
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die("command '%s' requested after already requesting command '%s'",
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out, (*command)->name);
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if (!cmd || !cmd->advertise(the_repository, NULL) || !cmd->command)
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die("invalid command '%s'", out);
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*command = cmd;
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return 1;
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}
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return 0;
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}
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int has_capability(const struct strvec *keys, const char *capability,
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const char **value)
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{
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int i;
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for (i = 0; i < keys->nr; i++) {
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const char *out;
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if (skip_prefix(keys->v[i], capability, &out) &&
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(!*out || *out == '=')) {
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if (value) {
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if (*out == '=')
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out++;
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*value = out;
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}
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return 1;
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}
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}
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return 0;
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}
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static void check_algorithm(struct repository *r, struct strvec *keys)
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{
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int client = GIT_HASH_SHA1, server = hash_algo_by_ptr(r->hash_algo);
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const char *algo_name;
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if (has_capability(keys, "object-format", &algo_name)) {
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client = hash_algo_by_name(algo_name);
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if (client == GIT_HASH_UNKNOWN)
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die("unknown object format '%s'", algo_name);
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}
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if (client != server)
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die("mismatched object format: server %s; client %s\n",
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r->hash_algo->name, hash_algos[client].name);
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}
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enum request_state {
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PROCESS_REQUEST_KEYS,
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PROCESS_REQUEST_DONE,
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};
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static int process_request(void)
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{
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enum request_state state = PROCESS_REQUEST_KEYS;
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struct packet_reader reader;
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struct strvec keys = STRVEC_INIT;
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struct protocol_capability *command = NULL;
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const char *client_sid;
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packet_reader_init(&reader, 0, NULL, 0,
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PACKET_READ_CHOMP_NEWLINE |
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PACKET_READ_GENTLE_ON_EOF |
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PACKET_READ_DIE_ON_ERR_PACKET);
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/*
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* Check to see if the client closed their end before sending another
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* request. If so we can terminate the connection.
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*/
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if (packet_reader_peek(&reader) == PACKET_READ_EOF)
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return 1;
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reader.options &= ~PACKET_READ_GENTLE_ON_EOF;
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while (state != PROCESS_REQUEST_DONE) {
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switch (packet_reader_peek(&reader)) {
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case PACKET_READ_EOF:
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BUG("Should have already died when seeing EOF");
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case PACKET_READ_NORMAL:
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/* collect request; a sequence of keys and values */
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if (is_command(reader.line, &command) ||
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is_valid_capability(reader.line))
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strvec_push(&keys, reader.line);
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else
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die("unknown capability '%s'", reader.line);
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/* Consume the peeked line */
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packet_reader_read(&reader);
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break;
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case PACKET_READ_FLUSH:
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/*
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* If no command and no keys were given then the client
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* wanted to terminate the connection.
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*/
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if (!keys.nr)
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return 1;
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/*
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* The flush packet isn't consume here like it is in
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* the other parts of this switch statement. This is
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* so that the command can read the flush packet and
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* see the end of the request in the same way it would
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* if command specific arguments were provided after a
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* delim packet.
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*/
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state = PROCESS_REQUEST_DONE;
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break;
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case PACKET_READ_DELIM:
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/* Consume the peeked line */
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packet_reader_read(&reader);
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state = PROCESS_REQUEST_DONE;
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break;
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case PACKET_READ_RESPONSE_END:
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BUG("unexpected stateless separator packet");
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}
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}
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if (!command)
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die("no command requested");
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check_algorithm(the_repository, &keys);
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if (has_capability(&keys, "session-id", &client_sid))
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trace2_data_string("transfer", NULL, "client-sid", client_sid);
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command->command(the_repository, &keys, &reader);
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strvec_clear(&keys);
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return 0;
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}
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/* Main serve loop for protocol version 2 */
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void serve(struct serve_options *options)
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{
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git_config_get_bool("transfer.advertisesid", &advertise_sid);
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if (options->advertise_capabilities || !options->stateless_rpc) {
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/* serve by default supports v2 */
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packet_write_fmt(1, "version 2\n");
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advertise_capabilities();
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/*
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* If only the list of capabilities was requested exit
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* immediately after advertising capabilities
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*/
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if (options->advertise_capabilities)
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return;
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}
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/*
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* If stateless-rpc was requested then exit after
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* a single request/response exchange
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*/
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if (options->stateless_rpc) {
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process_request();
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} else {
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for (;;)
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if (process_request())
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break;
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}
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}
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