Files
git/environment.c
Jeff King 27344d6a6c git: add --no-optional-locks option
Some tools like IDEs or fancy editors may periodically run
commands like "git status" in the background to keep track
of the state of the repository. Some of these commands may
refresh the index and write out the result in an
opportunistic way: if they can get the index lock, then they
update the on-disk index with any updates they find. And if
not, then their in-core refresh is lost and just has to be
recomputed by the next caller.

But taking the index lock may conflict with other operations
in the repository. Especially ones that the user is doing
themselves, which _aren't_ opportunistic. In other words,
"git status" knows how to back off when somebody else is
holding the lock, but other commands don't know that status
would be happy to drop the lock if somebody else wanted it.

There are a couple possible solutions:

  1. Have some kind of "pseudo-lock" that allows other
     commands to tell status that they want the lock.

     This is likely to be complicated and error-prone to
     implement (and maybe even impossible with just
     dotlocks to work from, as it requires some
     inter-process communication).

  2. Avoid background runs of commands like "git status"
     that want to do opportunistic updates, preferring
     instead plumbing like diff-files, etc.

     This is awkward for a couple of reasons. One is that
     "status --porcelain" reports a lot more about the
     repository state than is available from individual
     plumbing commands. And two is that we actually _do_
     want to see the refreshed index. We just don't want to
     take a lock or write out the result. Whereas commands
     like diff-files expect us to refresh the index
     separately and write it to disk so that they can depend
     on the result. But that write is exactly what we're
     trying to avoid.

  3. Ask "status" not to lock or write the index.

     This is easy to implement. The big downside is that any
     work done in refreshing the index for such a call is
     lost when the process exits. So a background process
     may end up re-hashing a changed file multiple times
     until the user runs a command that does an index
     refresh themselves.

This patch implements the option 3. The idea (and the test)
is largely stolen from a Git for Windows patch by Johannes
Schindelin, 67e5ce7f63 (status: offer *not* to lock the
index and update it, 2016-08-12). The twist here is that
instead of making this an option to "git status", it becomes
a "git" option and matching environment variable.

The reason there is two-fold:

  1. An environment variable is carried through to
     sub-processes. And whether an invocation is a
     background process or not should apply to the whole
     process tree. So you could do "git --no-optional-locks
     foo", and if "foo" is a script or alias that calls
     "status", you'll still get the effect.

  2. There may be other programs that want the same
     treatment.

     I've punted here on finding more callers to convert,
     since "status" is the obvious one to call as a repeated
     background job. But "git diff"'s opportunistic refresh
     of the index may be a good candidate.

The test is taken from 67e5ce7f63, and it's worth repeating
Johannes's explanation:

  Note that the regression test added in this commit does
  not *really* verify that no index.lock file was written;
  that test is not possible in a portable way. Instead, we
  verify that .git/index is rewritten *only* when `git
  status` is run without `--no-optional-locks`.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2017-09-27 16:11:01 +09:00

344 lines
8.9 KiB
C

/*
* We put all the git config variables in this same object
* file, so that programs can link against the config parser
* without having to link against all the rest of git.
*
* In particular, no need to bring in libz etc unless needed,
* even if you might want to know where the git directory etc
* are.
*/
#include "cache.h"
#include "repository.h"
#include "config.h"
#include "refs.h"
#include "fmt-merge-msg.h"
#include "commit.h"
int trust_executable_bit = 1;
int trust_ctime = 1;
int check_stat = 1;
int has_symlinks = 1;
int minimum_abbrev = 4, default_abbrev = -1;
int ignore_case;
int assume_unchanged;
int prefer_symlink_refs;
int is_bare_repository_cfg = -1; /* unspecified */
int warn_ambiguous_refs = 1;
int warn_on_object_refname_ambiguity = 1;
int ref_paranoia = -1;
int repository_format_precious_objects;
const char *git_commit_encoding;
const char *git_log_output_encoding;
const char *apply_default_whitespace;
const char *apply_default_ignorewhitespace;
const char *git_attributes_file;
const char *git_hooks_path;
int zlib_compression_level = Z_BEST_SPEED;
int core_compression_level;
int pack_compression_level = Z_DEFAULT_COMPRESSION;
int fsync_object_files;
size_t packed_git_window_size = DEFAULT_PACKED_GIT_WINDOW_SIZE;
size_t packed_git_limit = DEFAULT_PACKED_GIT_LIMIT;
size_t delta_base_cache_limit = 96 * 1024 * 1024;
unsigned long big_file_threshold = 512 * 1024 * 1024;
int pager_use_color = 1;
const char *editor_program;
const char *askpass_program;
const char *excludes_file;
enum auto_crlf auto_crlf = AUTO_CRLF_FALSE;
int check_replace_refs = 1;
char *git_replace_ref_base;
enum eol core_eol = EOL_UNSET;
enum safe_crlf safe_crlf = SAFE_CRLF_WARN;
unsigned whitespace_rule_cfg = WS_DEFAULT_RULE;
enum branch_track git_branch_track = BRANCH_TRACK_REMOTE;
enum rebase_setup_type autorebase = AUTOREBASE_NEVER;
enum push_default_type push_default = PUSH_DEFAULT_UNSPECIFIED;
#ifndef OBJECT_CREATION_MODE
#define OBJECT_CREATION_MODE OBJECT_CREATION_USES_HARDLINKS
#endif
enum object_creation_mode object_creation_mode = OBJECT_CREATION_MODE;
char *notes_ref_name;
int grafts_replace_parents = 1;
int core_apply_sparse_checkout;
int merge_log_config = -1;
int precomposed_unicode = -1; /* see probe_utf8_pathname_composition() */
unsigned long pack_size_limit_cfg;
enum hide_dotfiles_type hide_dotfiles = HIDE_DOTFILES_DOTGITONLY;
enum log_refs_config log_all_ref_updates = LOG_REFS_UNSET;
#ifndef PROTECT_HFS_DEFAULT
#define PROTECT_HFS_DEFAULT 0
#endif
int protect_hfs = PROTECT_HFS_DEFAULT;
#ifndef PROTECT_NTFS_DEFAULT
#define PROTECT_NTFS_DEFAULT 0
#endif
int protect_ntfs = PROTECT_NTFS_DEFAULT;
/*
* The character that begins a commented line in user-editable file
* that is subject to stripspace.
*/
char comment_line_char = '#';
int auto_comment_line_char;
/* Parallel index stat data preload? */
int core_preload_index = 1;
/*
* This is a hack for test programs like test-dump-untracked-cache to
* ensure that they do not modify the untracked cache when reading it.
* Do not use it otherwise!
*/
int ignore_untracked_cache_config;
/* This is set by setup_git_dir_gently() and/or git_default_config() */
char *git_work_tree_cfg;
static const char *namespace;
static const char *super_prefix;
/*
* Repository-local GIT_* environment variables; see cache.h for details.
*/
const char * const local_repo_env[] = {
ALTERNATE_DB_ENVIRONMENT,
CONFIG_ENVIRONMENT,
CONFIG_DATA_ENVIRONMENT,
DB_ENVIRONMENT,
GIT_DIR_ENVIRONMENT,
GIT_WORK_TREE_ENVIRONMENT,
GIT_IMPLICIT_WORK_TREE_ENVIRONMENT,
GRAFT_ENVIRONMENT,
INDEX_ENVIRONMENT,
NO_REPLACE_OBJECTS_ENVIRONMENT,
GIT_REPLACE_REF_BASE_ENVIRONMENT,
GIT_PREFIX_ENVIRONMENT,
GIT_SUPER_PREFIX_ENVIRONMENT,
GIT_SHALLOW_FILE_ENVIRONMENT,
GIT_COMMON_DIR_ENVIRONMENT,
NULL
};
static char *expand_namespace(const char *raw_namespace)
{
struct strbuf buf = STRBUF_INIT;
struct strbuf **components, **c;
if (!raw_namespace || !*raw_namespace)
return xstrdup("");
strbuf_addstr(&buf, raw_namespace);
components = strbuf_split(&buf, '/');
strbuf_reset(&buf);
for (c = components; *c; c++)
if (strcmp((*c)->buf, "/") != 0)
strbuf_addf(&buf, "refs/namespaces/%s", (*c)->buf);
strbuf_list_free(components);
if (check_refname_format(buf.buf, 0))
die("bad git namespace path \"%s\"", raw_namespace);
strbuf_addch(&buf, '/');
return strbuf_detach(&buf, NULL);
}
void setup_git_env(void)
{
const char *shallow_file;
const char *replace_ref_base;
if (getenv(NO_REPLACE_OBJECTS_ENVIRONMENT))
check_replace_refs = 0;
replace_ref_base = getenv(GIT_REPLACE_REF_BASE_ENVIRONMENT);
git_replace_ref_base = xstrdup(replace_ref_base ? replace_ref_base
: "refs/replace/");
namespace = expand_namespace(getenv(GIT_NAMESPACE_ENVIRONMENT));
shallow_file = getenv(GIT_SHALLOW_FILE_ENVIRONMENT);
if (shallow_file)
set_alternate_shallow_file(shallow_file, 0);
}
int is_bare_repository(void)
{
/* if core.bare is not 'false', let's see if there is a work tree */
return is_bare_repository_cfg && !get_git_work_tree();
}
int have_git_dir(void)
{
return startup_info->have_repository
|| the_repository->gitdir;
}
const char *get_git_dir(void)
{
if (!the_repository->gitdir)
BUG("git environment hasn't been setup");
return the_repository->gitdir;
}
const char *get_git_common_dir(void)
{
if (!the_repository->commondir)
BUG("git environment hasn't been setup");
return the_repository->commondir;
}
const char *get_git_namespace(void)
{
if (!namespace)
BUG("git environment hasn't been setup");
return namespace;
}
const char *strip_namespace(const char *namespaced_ref)
{
const char *out;
if (skip_prefix(namespaced_ref, get_git_namespace(), &out))
return out;
return NULL;
}
const char *get_super_prefix(void)
{
static int initialized;
if (!initialized) {
super_prefix = getenv(GIT_SUPER_PREFIX_ENVIRONMENT);
initialized = 1;
}
return super_prefix;
}
static int git_work_tree_initialized;
/*
* Note. This works only before you used a work tree. This was added
* primarily to support git-clone to work in a new repository it just
* created, and is not meant to flip between different work trees.
*/
void set_git_work_tree(const char *new_work_tree)
{
if (git_work_tree_initialized) {
new_work_tree = real_path(new_work_tree);
if (strcmp(new_work_tree, the_repository->worktree))
die("internal error: work tree has already been set\n"
"Current worktree: %s\nNew worktree: %s",
the_repository->worktree, new_work_tree);
return;
}
git_work_tree_initialized = 1;
repo_set_worktree(the_repository, new_work_tree);
}
const char *get_git_work_tree(void)
{
return the_repository->worktree;
}
char *get_object_directory(void)
{
if (!the_repository->objectdir)
BUG("git environment hasn't been setup");
return the_repository->objectdir;
}
int odb_mkstemp(struct strbuf *template, const char *pattern)
{
int fd;
/*
* we let the umask do its job, don't try to be more
* restrictive except to remove write permission.
*/
int mode = 0444;
git_path_buf(template, "objects/%s", pattern);
fd = git_mkstemp_mode(template->buf, mode);
if (0 <= fd)
return fd;
/* slow path */
/* some mkstemp implementations erase template on failure */
git_path_buf(template, "objects/%s", pattern);
safe_create_leading_directories(template->buf);
return xmkstemp_mode(template->buf, mode);
}
int odb_pack_keep(const char *name)
{
int fd;
fd = open(name, O_RDWR|O_CREAT|O_EXCL, 0600);
if (0 <= fd)
return fd;
/* slow path */
safe_create_leading_directories_const(name);
return open(name, O_RDWR|O_CREAT|O_EXCL, 0600);
}
char *get_index_file(void)
{
if (!the_repository->index_file)
BUG("git environment hasn't been setup");
return the_repository->index_file;
}
char *get_graft_file(void)
{
if (!the_repository->graft_file)
BUG("git environment hasn't been setup");
return the_repository->graft_file;
}
int set_git_dir(const char *path)
{
if (setenv(GIT_DIR_ENVIRONMENT, path, 1))
return error("Could not set GIT_DIR to '%s'", path);
repo_set_gitdir(the_repository, path);
setup_git_env();
return 0;
}
const char *get_log_output_encoding(void)
{
return git_log_output_encoding ? git_log_output_encoding
: get_commit_output_encoding();
}
const char *get_commit_output_encoding(void)
{
return git_commit_encoding ? git_commit_encoding : "UTF-8";
}
static int the_shared_repository = PERM_UMASK;
static int need_shared_repository_from_config = 1;
void set_shared_repository(int value)
{
the_shared_repository = value;
need_shared_repository_from_config = 0;
}
int get_shared_repository(void)
{
if (need_shared_repository_from_config) {
const char *var = "core.sharedrepository";
const char *value;
if (!git_config_get_value(var, &value))
the_shared_repository = git_config_perm(var, value);
need_shared_repository_from_config = 0;
}
return the_shared_repository;
}
void reset_shared_repository(void)
{
need_shared_repository_from_config = 1;
}
int use_optional_locks(void)
{
return git_env_bool(GIT_OPTIONAL_LOCKS_ENVIRONMENT, 1);
}