@matheusbsbs / matheus-bagliano / commits / 58a646a368

fetch: extract writing to FETCH_HEAD

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 <ps@pks.im> Signed-off-by: Junio C Hamano <gitster@pobox.com>

Patrick Steinhardt committed Jan 12, 2021 at 13:27 UTC 58a646a3688ea3c15adaf481e440e9ca2d3bce06

2 files changed +80 -30

builtin/fetch.c

+79 -29

@@ -897,6 +897,73 @@ static int iterate_ref_map(void *cb_data, struct object_id *oid)

897 return 0;

898 }

899

900 +struct fetch_head {

901 + FILE *fp;

902 +};

903 +

904 +static int open_fetch_head(struct fetch_head *fetch_head)

905 +{

906 + const char *filename = git_path_fetch_head(the_repository);

907 +

908 + if (write_fetch_head) {

909 + fetch_head->fp = fopen(filename, "a");

910 + if (!fetch_head->fp)

911 + return error_errno(_("cannot open %s"), filename);

912 + } else {

913 + fetch_head->fp = NULL;

914 + }

915 +

916 + return 0;

917 +}

918 +

919 +static void append_fetch_head(struct fetch_head *fetch_head,

920 + const struct object_id *old_oid,

921 + enum fetch_head_status fetch_head_status,

922 + const char *note,

923 + const char *url, size_t url_len)

924 +{

925 + char old_oid_hex[GIT_MAX_HEXSZ + 1];

926 + const char *merge_status_marker;

927 + size_t i;

928 +

929 + if (!fetch_head->fp)

930 + return;

931 +

932 + switch (fetch_head_status) {

933 + case FETCH_HEAD_NOT_FOR_MERGE:

934 + merge_status_marker = "not-for-merge";

935 + break;

936 + case FETCH_HEAD_MERGE:

937 + merge_status_marker = "";

938 + break;

939 + default:

940 + /* do not write anything to FETCH_HEAD */

941 + return;

942 + }

943 +

944 + fprintf(fetch_head->fp, "%s\t%s\t%s",

945 + oid_to_hex_r(old_oid_hex, old_oid), merge_status_marker, note);

946 + for (i = 0; i < url_len; ++i)

947 + if ('\n' == url[i])

948 + fputs("\\n", fetch_head->fp);

949 + else

950 + fputc(url[i], fetch_head->fp);

951 + fputc('\n', fetch_head->fp);

952 +}

953 +

954 +static void commit_fetch_head(struct fetch_head *fetch_head)

955 +{

956 + /* Nothing to commit yet. */

957 +}

958 +

959 +static void close_fetch_head(struct fetch_head *fetch_head)

960 +{

961 + if (!fetch_head->fp)

962 + return;

963 +

964 + fclose(fetch_head->fp);

965 +}

966 +

967 static const char warn_show_forced_updates[] =

968 N_("Fetch normally indicates which branches had a forced update,\n"

969 "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"

976 static int store_updated_refs(const char *raw_url, const char *remote_name,

977 int connectivity_checked, struct ref *ref_map)

978 {

912 - FILE *fp;

979 + struct fetch_head fetch_head;

980 struct commit *commit;

981 int url_len, i, rc = 0;

982 struct strbuf note = STRBUF_INIT;

983 const char *what, *kind;

984 struct ref *rm;

985 char *url;

919 - const char *filename = (!write_fetch_head

920 - ? "/dev/null"

921 - : git_path_fetch_head(the_repository));

986 int want_status;

987 int summary_width = transport_summary_width(ref_map);

988

925 - fp = fopen(filename, "a");

926 - if (!fp)

927 - return error_errno(_("cannot open %s"), filename);

989 + rc = open_fetch_head(&fetch_head);

990 + if (rc)

991 + return -1;

992

993 if (raw_url)

994 url = transport_anonymize_url(raw_url);

@@ -953,7 +1017,6 @@ static int store_updated_refs(const char *raw_url, const char *remote_name,

1017 want_status++) {

1018 for (rm = ref_map; rm; rm = rm->next) {

1019 struct ref *ref = NULL;

956 - const char *merge_status_marker = "";

1020

1021 if (rm->status == REF_STATUS_REJECT_SHALLOW) {

1022 if (want_status == FETCH_HEAD_MERGE)

@@ -1011,26 +1074,10 @@ static int store_updated_refs(const char *raw_url, const char *remote_name,

1074 strbuf_addf(&note, "%s ", kind);

1075 strbuf_addf(&note, "'%s' of ", what);

1076 }

1014 - switch (rm->fetch_head_status) {

1015 - case FETCH_HEAD_NOT_FOR_MERGE:

1016 - merge_status_marker = "not-for-merge";

1017 - /* fall-through */

1018 - case FETCH_HEAD_MERGE:

1019 - fprintf(fp, "%s\t%s\t%s",

1020 - oid_to_hex(&rm->old_oid),

1021 - merge_status_marker,

1022 - note.buf);

1023 - for (i = 0; i < url_len; ++i)

1024 - if ('\n' == url[i])

1025 - fputs("\\n", fp);

1026 - else

1027 - fputc(url[i], fp);

1028 - fputc('\n', fp);

1029 - break;

1030 - default:

1031 - /* do not write anything to FETCH_HEAD */

1032 - break;

1033 - }

1077 +

1078 + append_fetch_head(&fetch_head, &rm->old_oid,

1079 + rm->fetch_head_status,

1080 + note.buf, url, url_len);

1081

1082 strbuf_reset(&note);

1083 if (ref) {

@@ -1060,6 +1107,9 @@ static int store_updated_refs(const char *raw_url, const char *remote_name,

1107 }

1108 }

1109

1110 + if (!rc)

1111 + commit_fetch_head(&fetch_head);

1112 +

1113 if (rc & STORE_REF_ERROR_DF_CONFLICT)

1114 error(_("some local refs could not be updated; try running\n"

1115 " '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,

1127 abort:

1128 strbuf_release(&note);

1129 free(url);

1080 - fclose(fp);

1130 + close_fetch_head(&fetch_head);

1131 return rc;

1132 }

1133

remote.h

+1 -1

@@ -134,7 +134,7 @@ struct ref {

134 * should be 0, so that xcalloc'd structures get it

135 * by default.

136 */

137 - enum {

137 + enum fetch_head_status {

138 FETCH_HEAD_MERGE = -1,

139 FETCH_HEAD_NOT_FOR_MERGE = 0,

140 FETCH_HEAD_IGNORE = 1