Revision d699676dda5fdf0996601006c3bac2a9c077a862 authored by Linus Torvalds on 10 August 2007, 19:31:20 UTC, committed by Junio C Hamano on 10 August 2007, 21:00:25 UTC
This trivially optimizes the two-way merge case of git-read-tree too,
which affects switching branches.

When you have tons and tons of files in your repository, but there are
only small differences in the branches (maybe just a couple of files
changed), the biggest cost of the branch switching was actually just the
index calculations.

This fixes it (timings for switching between the "testing" and "master"
branches in the 100,000 file testing-repo-from-hell, where the branches
only differ in one small file).

Before:
	[torvalds@woody bummer]$ time git checkout master
	real    0m9.919s
	user    0m8.461s
	sys     0m0.264s

After:
	[torvalds@woody bummer]$ time git checkout testing
	real    0m0.576s
	user    0m0.348s
	sys     0m0.228s

so it's easily an order of magnitude different.

This concludes the series. I think we could/should do the three-way merge
too (to speed up merges), but I'm lazy. Somebody else can do it.

The rule is very simple: you need to remove the old entry if:
 - you want to remove the file entirely
 - you replace it with a "merge conflict" entry (ie a non-stage-0 entry)

and you can avoid removing it if you either

 - keep the old one
 - or resolve it to a new one.

and these rules should all be valid for the three-way case too.

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
1 parent 288f072
Raw File
environment.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"

char git_default_email[MAX_GITNAME];
char git_default_name[MAX_GITNAME];
int trust_executable_bit = 1;
int quote_path_fully = 1;
int has_symlinks = 1;
int assume_unchanged;
int prefer_symlink_refs;
int is_bare_repository_cfg = -1; /* unspecified */
int log_all_ref_updates = -1; /* unspecified */
int warn_ambiguous_refs = 1;
int repository_format_version;
const char *git_commit_encoding;
const char *git_log_output_encoding;
int shared_repository = PERM_UMASK;
const char *apply_default_whitespace;
int zlib_compression_level = Z_BEST_SPEED;
int core_compression_level;
int core_compression_seen;
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 = 16 * 1024 * 1024;
char *pager_program;
int pager_in_use;
int pager_use_color = 1;
int auto_crlf = 0;	/* 1: both ways, -1: only when adding git objects */

/* This is set by setup_git_dir_gently() and/or git_default_config() */
char *git_work_tree_cfg;
static const char *work_tree;

static const char *git_dir;
static char *git_object_dir, *git_index_file, *git_refs_dir, *git_graft_file;

static void setup_git_env(void)
{
	git_dir = getenv(GIT_DIR_ENVIRONMENT);
	if (!git_dir)
		git_dir = DEFAULT_GIT_DIR_ENVIRONMENT;
	git_object_dir = getenv(DB_ENVIRONMENT);
	if (!git_object_dir) {
		git_object_dir = xmalloc(strlen(git_dir) + 9);
		sprintf(git_object_dir, "%s/objects", git_dir);
	}
	git_refs_dir = xmalloc(strlen(git_dir) + 6);
	sprintf(git_refs_dir, "%s/refs", git_dir);
	git_index_file = getenv(INDEX_ENVIRONMENT);
	if (!git_index_file) {
		git_index_file = xmalloc(strlen(git_dir) + 7);
		sprintf(git_index_file, "%s/index", git_dir);
	}
	git_graft_file = getenv(GRAFT_ENVIRONMENT);
	if (!git_graft_file)
		git_graft_file = xstrdup(git_path("info/grafts"));
}

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();
}

const char *get_git_dir(void)
{
	if (!git_dir)
		setup_git_env();
	return git_dir;
}

const char *get_git_work_tree(void)
{
	static int initialized = 0;
	if (!initialized) {
		work_tree = getenv(GIT_WORK_TREE_ENVIRONMENT);
		/* core.bare = true overrides implicit and config work tree */
		if (!work_tree && is_bare_repository_cfg < 1) {
			work_tree = git_work_tree_cfg;
			/* make_absolute_path also normalizes the path */
			if (work_tree && !is_absolute_path(work_tree))
				work_tree = xstrdup(make_absolute_path(git_path(work_tree)));
		} else if (work_tree)
			work_tree = xstrdup(make_absolute_path(work_tree));
		initialized = 1;
		if (work_tree)
			is_bare_repository_cfg = 0;
	}
	return work_tree;
}

char *get_object_directory(void)
{
	if (!git_object_dir)
		setup_git_env();
	return git_object_dir;
}

char *get_refs_directory(void)
{
	if (!git_refs_dir)
		setup_git_env();
	return git_refs_dir;
}

char *get_index_file(void)
{
	if (!git_index_file)
		setup_git_env();
	return git_index_file;
}

char *get_graft_file(void)
{
	if (!git_graft_file)
		setup_git_env();
	return git_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);
	setup_git_env();
	return 0;
}
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