When performing a fetch with the default `--write-fetch-head` option, we write all updated references to FETCH_HEAD while the updates are performed. Given that updates are not performed atomically, it means that we we write to FETCH_HEAD even if some or all of the reference updates fail. Given that we simply update FETCH_HEAD ad-hoc with each reference, the logic is completely contained in `store_update_refs` and thus quite hard to extend. This can already be seen by the way we skip writing to the FETCH_HEAD: instead of having a conditional which simply skips writing, we instead open "/dev/null" and needlessly write all updates there. We are about to extend git-fetch(1) to accept an `--atomic` flag which will make the fetch an all-or-nothing operation with regards to the reference updates. This will also require us to make the updates to FETCH_HEAD an all-or-nothing operation, but as explained doing so is not easy with the current layout. This commit thus refactors the wa we write to FETCH_HEAD and pulls out the logic to open, append to, commit and close the file. While this may seem rather over-the top at first, pulling out this logic will make it a lot easier to update the code in a subsequent commit. It also allows us to easily skip writing completely in case `--no-write-fetch-head` was passed. Signed-off-by: Patrick Steinhardt --- builtin/fetch.c | 108 +++++++++++++++++++++++++++++++++++------------- remote.h | 2 +- 2 files changed, 80 insertions(+), 30 deletions(-) diff --git a/builtin/fetch.c b/builtin/fetch.c index ecf8537605..2dd5fcb652 100644 --- a/builtin/fetch.c +++ b/builtin/fetch.c @@ -897,6 +897,73 @@ static int iterate_ref_map(void *cb_data, struct object_id *oid) return 0; } +struct fetch_head { + FILE *fp; +}; + +static int open_fetch_head(struct fetch_head *fetch_head) +{ + const char *filename = git_path_fetch_head(the_repository); + + if (write_fetch_head) { + fetch_head->fp = fopen(filename, "a"); + if (!fetch_head->fp) + return error_errno(_("cannot open %s"), filename); + } else { + fetch_head->fp = NULL; + } + + return 0; +} + +static void append_fetch_head(struct fetch_head *fetch_head, + const struct object_id *old_oid, + enum fetch_head_status fetch_head_status, + const char *note, + const char *url, size_t url_len) +{ + char old_oid_hex[GIT_MAX_HEXSZ + 1]; + const char *merge_status_marker; + size_t i; + + if (!fetch_head->fp) + return; + + switch (fetch_head_status) { + case FETCH_HEAD_NOT_FOR_MERGE: + merge_status_marker = "not-for-merge"; + break; + case FETCH_HEAD_MERGE: + merge_status_marker = ""; + break; + default: + /* do not write anything to FETCH_HEAD */ + return; + } + + fprintf(fetch_head->fp, "%s\t%s\t%s", + oid_to_hex_r(old_oid_hex, old_oid), merge_status_marker, note); + for (i = 0; i < url_len; ++i) + if ('\n' == url[i]) + fputs("\\n", fetch_head->fp); + else + fputc(url[i], fetch_head->fp); + fputc('\n', fetch_head->fp); +} + +static void commit_fetch_head(struct fetch_head *fetch_head) +{ + /* Nothing to commit yet. */ +} + +static void close_fetch_head(struct fetch_head *fetch_head) +{ + if (!fetch_head->fp) + return; + + fclose(fetch_head->fp); +} + static const char warn_show_forced_updates[] = N_("Fetch normally indicates which branches had a forced update,\n" "but that check has been disabled. To re-enable, use '--show-forced-updates'\n" @@ -909,22 +976,19 @@ N_("It took %.2f seconds to check forced updates. You can use\n" static int store_updated_refs(const char *raw_url, const char *remote_name, int connectivity_checked, struct ref *ref_map) { - FILE *fp; + struct fetch_head fetch_head; struct commit *commit; int url_len, i, rc = 0; struct strbuf note = STRBUF_INIT; const char *what, *kind; struct ref *rm; char *url; - const char *filename = (!write_fetch_head - ? "/dev/null" - : git_path_fetch_head(the_repository)); int want_status; int summary_width = transport_summary_width(ref_map); - fp = fopen(filename, "a"); - if (!fp) - return error_errno(_("cannot open %s"), filename); + rc = open_fetch_head(&fetch_head); + if (rc) + return -1; if (raw_url) url = transport_anonymize_url(raw_url); @@ -953,7 +1017,6 @@ static int store_updated_refs(const char *raw_url, const char *remote_name, want_status++) { for (rm = ref_map; rm; rm = rm->next) { struct ref *ref = NULL; - const char *merge_status_marker = ""; if (rm->status == REF_STATUS_REJECT_SHALLOW) { if (want_status == FETCH_HEAD_MERGE) @@ -1011,26 +1074,10 @@ static int store_updated_refs(const char *raw_url, const char *remote_name, strbuf_addf(¬e, "%s ", kind); strbuf_addf(¬e, "'%s' of ", what); } - switch (rm->fetch_head_status) { - case FETCH_HEAD_NOT_FOR_MERGE: - merge_status_marker = "not-for-merge"; - /* fall-through */ - case FETCH_HEAD_MERGE: - fprintf(fp, "%s\t%s\t%s", - oid_to_hex(&rm->old_oid), - merge_status_marker, - note.buf); - for (i = 0; i < url_len; ++i) - if ('\n' == url[i]) - fputs("\\n", fp); - else - fputc(url[i], fp); - fputc('\n', fp); - break; - default: - /* do not write anything to FETCH_HEAD */ - break; - } + + append_fetch_head(&fetch_head, &rm->old_oid, + rm->fetch_head_status, + note.buf, url, url_len); strbuf_reset(¬e); if (ref) { @@ -1060,6 +1107,9 @@ static int store_updated_refs(const char *raw_url, const char *remote_name, } } + if (!rc) + commit_fetch_head(&fetch_head); + if (rc & STORE_REF_ERROR_DF_CONFLICT) error(_("some local refs could not be updated; try running\n" " 'git remote prune %s' to remove any old, conflicting " @@ -1077,7 +1127,7 @@ static int store_updated_refs(const char *raw_url, const char *remote_name, abort: strbuf_release(¬e); free(url); - fclose(fp); + close_fetch_head(&fetch_head); return rc; } diff --git a/remote.h b/remote.h index 3211abdf05..aad1a0f080 100644 --- a/remote.h +++ b/remote.h @@ -134,7 +134,7 @@ struct ref { * should be 0, so that xcalloc'd structures get it * by default. */ - enum { + enum fetch_head_status { FETCH_HEAD_MERGE = -1, FETCH_HEAD_NOT_FOR_MERGE = 0, FETCH_HEAD_IGNORE = 1 -- 2.30.0