update-server-info: avoid needless overwrites
Do not change the existing info/refs and objects/info/packs
files if they match the existing content on the filesystem.
This is intended to preserve mtime and make it easier for dumb
HTTP pollers to rely on the If-Modified-Since header.
Combined with stdio and kernel buffering; the kernel should be
able to avoid block layer writes and reduce wear for small files.
As a result, the --force option is no longer needed. So stop
documenting it, but let it remain for compatibility (and
debugging, if necessary).
v3: perform incremental comparison while generating to avoid
OOM with giant files. Remove documentation for --force.
Signed-off-by: Eric Wong <e@80x24.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This commit is contained in:
Eric Wong
Junio C Hamano
parent
ab15ad1a3b
commit
f4f476b6a1
@ -9,7 +9,7 @@ git-update-server-info - Update auxiliary info file to help dumb servers
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SYNOPSIS
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--------
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[verse]
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'git update-server-info' [--force]
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'git update-server-info'
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DESCRIPTION
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-----------
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@ -19,15 +19,6 @@ $GIT_OBJECT_DIRECTORY/info directories to help clients discover
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what references and packs the server has. This command
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generates such auxiliary files.
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OPTIONS
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-------
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-f::
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--force::
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Update the info files from scratch.
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OUTPUT
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------
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140
server-info.c
140
server-info.c
@ -6,82 +6,174 @@
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#include "tag.h"
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#include "packfile.h"
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#include "object-store.h"
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#include "strbuf.h"
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struct update_info_ctx {
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FILE *cur_fp;
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FILE *old_fp; /* becomes NULL if it differs from cur_fp */
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struct strbuf cur_sb;
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struct strbuf old_sb;
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};
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static void uic_mark_stale(struct update_info_ctx *uic)
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{
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fclose(uic->old_fp);
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uic->old_fp = NULL;
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}
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static int uic_is_stale(const struct update_info_ctx *uic)
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{
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return uic->old_fp == NULL;
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}
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static int uic_printf(struct update_info_ctx *uic, const char *fmt, ...)
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{
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va_list ap;
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int ret = -1;
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va_start(ap, fmt);
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if (uic_is_stale(uic)) {
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ret = vfprintf(uic->cur_fp, fmt, ap);
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} else {
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ssize_t r;
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struct strbuf *cur = &uic->cur_sb;
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struct strbuf *old = &uic->old_sb;
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strbuf_reset(cur);
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strbuf_vinsertf(cur, 0, fmt, ap);
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strbuf_reset(old);
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strbuf_grow(old, cur->len);
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r = fread(old->buf, 1, cur->len, uic->old_fp);
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if (r != cur->len || memcmp(old->buf, cur->buf, r))
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uic_mark_stale(uic);
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if (fwrite(cur->buf, 1, cur->len, uic->cur_fp) == cur->len)
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ret = 0;
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}
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va_end(ap);
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return ret;
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}
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/*
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* Create the file "path" by writing to a temporary file and renaming
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* it into place. The contents of the file come from "generate", which
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* should return non-zero if it encounters an error.
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*/
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static int update_info_file(char *path, int (*generate)(FILE *))
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static int update_info_file(char *path,
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int (*generate)(struct update_info_ctx *),
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int force)
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{
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char *tmp = mkpathdup("%s_XXXXXX", path);
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int ret = -1;
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int fd = -1;
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FILE *fp = NULL, *to_close;
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FILE *to_close;
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struct update_info_ctx uic = {
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.cur_fp = NULL,
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.old_fp = NULL,
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.cur_sb = STRBUF_INIT,
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.old_sb = STRBUF_INIT
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};
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safe_create_leading_directories(path);
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fd = git_mkstemp_mode(tmp, 0666);
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if (fd < 0)
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goto out;
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to_close = fp = fdopen(fd, "w");
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if (!fp)
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to_close = uic.cur_fp = fdopen(fd, "w");
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if (!uic.cur_fp)
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goto out;
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fd = -1;
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ret = generate(fp);
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/* no problem on ENOENT and old_fp == NULL, it's stale, now */
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if (!force)
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uic.old_fp = fopen_or_warn(path, "r");
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/*
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* uic_printf will compare incremental comparison aginst old_fp
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* and mark uic as stale if needed
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*/
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ret = generate(&uic);
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if (ret)
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goto out;
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fp = NULL;
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/* new file may be shorter than the old one, check here */
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if (!uic_is_stale(&uic)) {
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struct stat st;
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long new_len = ftell(uic.cur_fp);
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int old_fd = fileno(uic.old_fp);
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if (new_len < 0) {
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ret = -1;
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goto out;
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}
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if (fstat(old_fd, &st) || (st.st_size != (size_t)new_len))
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uic_mark_stale(&uic);
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}
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uic.cur_fp = NULL;
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if (fclose(to_close))
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goto out;
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if (adjust_shared_perm(tmp) < 0)
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goto out;
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if (rename(tmp, path) < 0)
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goto out;
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if (uic_is_stale(&uic)) {
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if (adjust_shared_perm(tmp) < 0)
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goto out;
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if (rename(tmp, path) < 0)
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goto out;
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} else {
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unlink(tmp);
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}
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ret = 0;
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out:
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if (ret) {
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error_errno("unable to update %s", path);
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if (fp)
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fclose(fp);
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if (uic.cur_fp)
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fclose(uic.cur_fp);
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else if (fd >= 0)
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close(fd);
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unlink(tmp);
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}
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free(tmp);
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if (uic.old_fp)
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fclose(uic.old_fp);
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strbuf_release(&uic.old_sb);
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strbuf_release(&uic.cur_sb);
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return ret;
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}
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static int add_info_ref(const char *path, const struct object_id *oid,
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int flag, void *cb_data)
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{
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FILE *fp = cb_data;
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struct update_info_ctx *uic = cb_data;
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struct object *o = parse_object(the_repository, oid);
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if (!o)
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return -1;
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if (fprintf(fp, "%s %s\n", oid_to_hex(oid), path) < 0)
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if (uic_printf(uic, "%s %s\n", oid_to_hex(oid), path) < 0)
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return -1;
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if (o->type == OBJ_TAG) {
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o = deref_tag(the_repository, o, path, 0);
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if (o)
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if (fprintf(fp, "%s %s^{}\n",
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if (uic_printf(uic, "%s %s^{}\n",
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oid_to_hex(&o->oid), path) < 0)
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return -1;
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}
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return 0;
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}
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static int generate_info_refs(FILE *fp)
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static int generate_info_refs(struct update_info_ctx *uic)
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{
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return for_each_ref(add_info_ref, fp);
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return for_each_ref(add_info_ref, uic);
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}
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static int update_info_refs(void)
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static int update_info_refs(int force)
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{
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char *path = git_pathdup("info/refs");
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int ret = update_info_file(path, generate_info_refs);
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int ret = update_info_file(path, generate_info_refs, force);
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free(path);
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return ret;
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}
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@ -236,14 +328,14 @@ static void free_pack_info(void)
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free(info);
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}
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static int write_pack_info_file(FILE *fp)
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static int write_pack_info_file(struct update_info_ctx *uic)
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{
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int i;
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for (i = 0; i < num_pack; i++) {
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if (fprintf(fp, "P %s\n", pack_basename(info[i]->p)) < 0)
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if (uic_printf(uic, "P %s\n", pack_basename(info[i]->p)) < 0)
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return -1;
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}
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if (fputc('\n', fp) == EOF)
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if (uic_printf(uic, "\n") < 0)
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return -1;
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return 0;
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}
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@ -254,7 +346,7 @@ static int update_info_packs(int force)
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int ret;
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init_pack_info(infofile, force);
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ret = update_info_file(infofile, write_pack_info_file);
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ret = update_info_file(infofile, write_pack_info_file, force);
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free_pack_info();
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free(infofile);
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return ret;
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@ -269,7 +361,7 @@ int update_server_info(int force)
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*/
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int errs = 0;
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errs = errs | update_info_refs();
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errs = errs | update_info_refs(force);
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errs = errs | update_info_packs(force);
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/* remove leftover rev-cache file if there is any */
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41
t/t5200-update-server-info.sh
Executable file
41
t/t5200-update-server-info.sh
Executable file
@ -0,0 +1,41 @@
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#!/bin/sh
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test_description='Test git update-server-info'
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. ./test-lib.sh
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test_expect_success 'setup' 'test_commit file'
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test_expect_success 'create info/refs' '
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git update-server-info &&
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test_path_is_file .git/info/refs
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'
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test_expect_success 'modify and store mtime' '
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test-tool chmtime =0 .git/info/refs &&
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test-tool chmtime --get .git/info/refs >a
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'
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test_expect_success 'info/refs is not needlessly overwritten' '
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git update-server-info &&
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test-tool chmtime --get .git/info/refs >b &&
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test_cmp a b
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'
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test_expect_success 'info/refs can be forced to update' '
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git update-server-info -f &&
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test-tool chmtime --get .git/info/refs >b &&
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! test_cmp a b
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'
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test_expect_success 'info/refs updates when changes are made' '
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test-tool chmtime =0 .git/info/refs &&
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test-tool chmtime --get .git/info/refs >b &&
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test_cmp a b &&
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git update-ref refs/heads/foo HEAD &&
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git update-server-info &&
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test-tool chmtime --get .git/info/refs >b &&
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! test_cmp a b
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'
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test_done
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