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authorJunio C Hamano <gitster@pobox.com>2015-11-03 23:32:25 (GMT)
committerJunio C Hamano <gitster@pobox.com>2015-11-03 23:32:25 (GMT)
commitf89baca1b99ff2882690d6b58dc2071195c6ae84 (patch)
tree2901be0d9c8d2b46710fe97681b66b116127fd96
parentb05c2f9ed48adfd9670b28ecdd5c55a4e4698704 (diff)
parent067fbd4105c5aa8260a73cc6961854be0e93fa03 (diff)
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Merge branch 'jk/repository-extension' into maint
Prepare for Git on-disk repository representation to undergo backward incompatible changes by introducing a new repository format version "1", with an extension mechanism. * jk/repository-extension: introduce "preciousObjects" repository extension introduce "extensions" form of core.repositoryformatversion
-rw-r--r--Documentation/technical/repository-version.txt88
-rw-r--r--builtin/gc.c20
-rw-r--r--builtin/prune.c3
-rw-r--r--builtin/repack.c3
-rw-r--r--cache.h7
-rw-r--r--environment.c1
-rw-r--r--setup.c39
-rwxr-xr-xt/t1302-repo-version.sh60
8 files changed, 209 insertions, 12 deletions
diff --git a/Documentation/technical/repository-version.txt b/Documentation/technical/repository-version.txt
new file mode 100644
index 0000000..00ad379
--- /dev/null
+++ b/Documentation/technical/repository-version.txt
@@ -0,0 +1,88 @@
+Git Repository Format Versions
+==============================
+
+Every git repository is marked with a numeric version in the
+`core.repositoryformatversion` key of its `config` file. This version
+specifies the rules for operating on the on-disk repository data. An
+implementation of git which does not understand a particular version
+advertised by an on-disk repository MUST NOT operate on that repository;
+doing so risks not only producing wrong results, but actually losing
+data.
+
+Because of this rule, version bumps should be kept to an absolute
+minimum. Instead, we generally prefer these strategies:
+
+ - bumping format version numbers of individual data files (e.g.,
+ index, packfiles, etc). This restricts the incompatibilities only to
+ those files.
+
+ - introducing new data that gracefully degrades when used by older
+ clients (e.g., pack bitmap files are ignored by older clients, which
+ simply do not take advantage of the optimization they provide).
+
+A whole-repository format version bump should only be part of a change
+that cannot be independently versioned. For instance, if one were to
+change the reachability rules for objects, or the rules for locking
+refs, that would require a bump of the repository format version.
+
+Note that this applies only to accessing the repository's disk contents
+directly. An older client which understands only format `0` may still
+connect via `git://` to a repository using format `1`, as long as the
+server process understands format `1`.
+
+The preferred strategy for rolling out a version bump (whether whole
+repository or for a single file) is to teach git to read the new format,
+and allow writing the new format with a config switch or command line
+option (for experimentation or for those who do not care about backwards
+compatibility with older gits). Then after a long period to allow the
+reading capability to become common, we may switch to writing the new
+format by default.
+
+The currently defined format versions are:
+
+Version `0`
+-----------
+
+This is the format defined by the initial version of git, including but
+not limited to the format of the repository directory, the repository
+configuration file, and the object and ref storage. Specifying the
+complete behavior of git is beyond the scope of this document.
+
+Version `1`
+-----------
+
+This format is identical to version `0`, with the following exceptions:
+
+ 1. When reading the `core.repositoryformatversion` variable, a git
+ implementation which supports version 1 MUST also read any
+ configuration keys found in the `extensions` section of the
+ configuration file.
+
+ 2. If a version-1 repository specifies any `extensions.*` keys that
+ the running git has not implemented, the operation MUST NOT
+ proceed. Similarly, if the value of any known key is not understood
+ by the implementation, the operation MUST NOT proceed.
+
+Note that if no extensions are specified in the config file, then
+`core.repositoryformatversion` SHOULD be set to `0` (setting it to `1`
+provides no benefit, and makes the repository incompatible with older
+implementations of git).
+
+This document will serve as the master list for extensions. Any
+implementation wishing to define a new extension should make a note of
+it here, in order to claim the name.
+
+The defined extensions are:
+
+`noop`
+~~~~~~
+
+This extension does not change git's behavior at all. It is useful only
+for testing format-1 compatibility.
+
+`preciousObjects`
+~~~~~~~~~~~~~~~~~
+
+When the config key `extensions.preciousObjects` is set to `true`,
+objects in the repository MUST NOT be deleted (e.g., by `git-prune` or
+`git repack -d`).
diff --git a/builtin/gc.c b/builtin/gc.c
index 0ad8d30..b757d9a 100644
--- a/builtin/gc.c
+++ b/builtin/gc.c
@@ -340,15 +340,17 @@ int cmd_gc(int argc, const char **argv, const char *prefix)
if (gc_before_repack())
return -1;
- if (run_command_v_opt(repack.argv, RUN_GIT_CMD))
- return error(FAILED_RUN, repack.argv[0]);
-
- if (prune_expire) {
- argv_array_push(&prune, prune_expire);
- if (quiet)
- argv_array_push(&prune, "--no-progress");
- if (run_command_v_opt(prune.argv, RUN_GIT_CMD))
- return error(FAILED_RUN, prune.argv[0]);
+ if (!repository_format_precious_objects) {
+ if (run_command_v_opt(repack.argv, RUN_GIT_CMD))
+ return error(FAILED_RUN, repack.argv[0]);
+
+ if (prune_expire) {
+ argv_array_push(&prune, prune_expire);
+ if (quiet)
+ argv_array_push(&prune, "--no-progress");
+ if (run_command_v_opt(prune.argv, RUN_GIT_CMD))
+ return error(FAILED_RUN, prune.argv[0]);
+ }
}
if (prune_worktrees_expire) {
diff --git a/builtin/prune.c b/builtin/prune.c
index 10b03d3..8f4f052 100644
--- a/builtin/prune.c
+++ b/builtin/prune.c
@@ -119,6 +119,9 @@ int cmd_prune(int argc, const char **argv, const char *prefix)
argc = parse_options(argc, argv, prefix, options, prune_usage, 0);
+ if (repository_format_precious_objects)
+ die(_("cannot prune in a precious-objects repo"));
+
while (argc--) {
unsigned char sha1[20];
const char *name = *argv++;
diff --git a/builtin/repack.c b/builtin/repack.c
index 70b9b1e..9456110 100644
--- a/builtin/repack.c
+++ b/builtin/repack.c
@@ -193,6 +193,9 @@ int cmd_repack(int argc, const char **argv, const char *prefix)
argc = parse_options(argc, argv, prefix, builtin_repack_options,
git_repack_usage, 0);
+ if (delete_redundant && repository_format_precious_objects)
+ die(_("cannot delete packs in a precious-objects repo"));
+
if (pack_kept_objects < 0)
pack_kept_objects = write_bitmaps;
diff --git a/cache.h b/cache.h
index 79066e5..d801429 100644
--- a/cache.h
+++ b/cache.h
@@ -696,8 +696,15 @@ extern char *notes_ref_name;
extern int grafts_replace_parents;
+/*
+ * GIT_REPO_VERSION is the version we write by default. The
+ * _READ variant is the highest number we know how to
+ * handle.
+ */
#define GIT_REPO_VERSION 0
+#define GIT_REPO_VERSION_READ 1
extern int repository_format_version;
+extern int repository_format_precious_objects;
extern int check_repository_format(void);
#define MTIME_CHANGED 0x0001
diff --git a/environment.c b/environment.c
index a533aed..23a38e4 100644
--- a/environment.c
+++ b/environment.c
@@ -26,6 +26,7 @@ int warn_ambiguous_refs = 1;
int warn_on_object_refname_ambiguity = 1;
int ref_paranoia = -1;
int repository_format_version;
+int repository_format_precious_objects;
const char *git_commit_encoding;
const char *git_log_output_encoding;
int shared_repository = PERM_UMASK;
diff --git a/setup.c b/setup.c
index a17c51e..3324014 100644
--- a/setup.c
+++ b/setup.c
@@ -5,6 +5,7 @@
static int inside_git_dir = -1;
static int inside_work_tree = -1;
static int work_tree_config_is_bogus;
+static struct string_list unknown_extensions = STRING_LIST_INIT_DUP;
/*
* The input parameter must contain an absolute path, and it must already be
@@ -352,10 +353,25 @@ void setup_work_tree(void)
static int check_repo_format(const char *var, const char *value, void *cb)
{
+ const char *ext;
+
if (strcmp(var, "core.repositoryformatversion") == 0)
repository_format_version = git_config_int(var, value);
else if (strcmp(var, "core.sharedrepository") == 0)
shared_repository = git_config_perm(var, value);
+ else if (skip_prefix(var, "extensions.", &ext)) {
+ /*
+ * record any known extensions here; otherwise,
+ * we fall through to recording it as unknown, and
+ * check_repository_format will complain
+ */
+ if (!strcmp(ext, "noop"))
+ ;
+ else if (!strcmp(ext, "preciousobjects"))
+ repository_format_precious_objects = git_config_bool(var, value);
+ else
+ string_list_append(&unknown_extensions, ext);
+ }
return 0;
}
@@ -366,6 +382,8 @@ static int check_repository_format_gently(const char *gitdir, int *nongit_ok)
config_fn_t fn;
int ret = 0;
+ string_list_clear(&unknown_extensions, 0);
+
if (get_common_dir(&sb, gitdir))
fn = check_repo_format;
else
@@ -383,16 +401,31 @@ static int check_repository_format_gently(const char *gitdir, int *nongit_ok)
* is a good one.
*/
git_config_early(fn, NULL, repo_config);
- if (GIT_REPO_VERSION < repository_format_version) {
+ if (GIT_REPO_VERSION_READ < repository_format_version) {
if (!nongit_ok)
die ("Expected git repo version <= %d, found %d",
- GIT_REPO_VERSION, repository_format_version);
+ GIT_REPO_VERSION_READ, repository_format_version);
warning("Expected git repo version <= %d, found %d",
- GIT_REPO_VERSION, repository_format_version);
+ GIT_REPO_VERSION_READ, repository_format_version);
warning("Please upgrade Git");
*nongit_ok = -1;
ret = -1;
}
+
+ if (repository_format_version >= 1 && unknown_extensions.nr) {
+ int i;
+
+ if (!nongit_ok)
+ die("unknown repository extension: %s",
+ unknown_extensions.items[0].string);
+
+ for (i = 0; i < unknown_extensions.nr; i++)
+ warning("unknown repository extension: %s",
+ unknown_extensions.items[i].string);
+ *nongit_ok = -1;
+ ret = -1;
+ }
+
strbuf_release(&sb);
return ret;
}
diff --git a/t/t1302-repo-version.sh b/t/t1302-repo-version.sh
index 0d9388a..9bcd349 100755
--- a/t/t1302-repo-version.sh
+++ b/t/t1302-repo-version.sh
@@ -67,4 +67,64 @@ test_expect_success 'gitdir required mode' '
)
'
+check_allow () {
+ git rev-parse --git-dir >actual &&
+ echo .git >expect &&
+ test_cmp expect actual
+}
+
+check_abort () {
+ test_must_fail git rev-parse --git-dir
+}
+
+# avoid git-config, since it cannot be trusted to run
+# in a repository with a broken version
+mkconfig () {
+ echo '[core]' &&
+ echo "repositoryformatversion = $1" &&
+ shift &&
+
+ if test $# -gt 0; then
+ echo '[extensions]' &&
+ for i in "$@"; do
+ echo "$i"
+ done
+ fi
+}
+
+while read outcome version extensions; do
+ test_expect_success "$outcome version=$version $extensions" "
+ mkconfig $version $extensions >.git/config &&
+ check_${outcome}
+ "
+done <<\EOF
+allow 0
+allow 1
+allow 1 noop
+abort 1 no-such-extension
+allow 0 no-such-extension
+EOF
+
+test_expect_success 'precious-objects allowed' '
+ mkconfig 1 preciousObjects >.git/config &&
+ check_allow
+'
+
+test_expect_success 'precious-objects blocks destructive repack' '
+ test_must_fail git repack -ad
+'
+
+test_expect_success 'other repacks are OK' '
+ test_commit foo &&
+ git repack
+'
+
+test_expect_success 'precious-objects blocks prune' '
+ test_must_fail git prune
+'
+
+test_expect_success 'gc runs without complaint' '
+ git gc
+'
+
test_done