checkout: optimize "git checkout -b <new_branch>"

Skip merging the commit, updating the index and working directory if and
only if we are creating a new branch via "git checkout -b <new_branch>."
Any other checkout options will still go through the former code path.

If sparse_checkout is on, require the user to manually opt in to this
optimzed behavior by setting the config setting checkout.optimizeNewBranch
to true as we will no longer update the skip-worktree bit in the index, nor
add/remove files in the working directory to reflect the current sparse
checkout settings.

For comparison, running "git checkout -b <new_branch>" on a large repo takes:

14.6 seconds - without this patch
0.3 seconds - with this patch

Signed-off-by: Ben Peart <Ben.Peart@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This commit is contained in:
Ben Peart 2018-08-16 18:27:11 +00:00 коммит произвёл Junio C Hamano
Родитель ffc6fa0e39
Коммит fa655d8411
3 изменённых файлов: 138 добавлений и 4 удалений

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@ -1101,6 +1101,14 @@ browser.<tool>.path::
browse HTML help (see `-w` option in linkgit:git-help[1]) or a
working repository in gitweb (see linkgit:git-instaweb[1]).
checkout.optimizeNewBranch
Optimizes the performance of "git checkout -b <new_branch>" when
using sparse-checkout. When set to true, git will not update the
repo based on the current sparse-checkout settings. This means it
will not update the skip-worktree bit in the index nor add/remove
files in the working directory to reflect the current sparse checkout
settings nor will it show the local changes.
clean.requireForce::
A boolean to make git-clean do nothing unless given -f,
-i or -n. Defaults to true.

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@ -24,6 +24,8 @@
#include "submodule-config.h"
#include "submodule.h"
static int checkout_optimize_new_branch;
static const char * const checkout_usage[] = {
N_("git checkout [<options>] <branch>"),
N_("git checkout [<options>] [<branch>] -- <file>..."),
@ -41,6 +43,10 @@ struct checkout_opts {
int ignore_skipworktree;
int ignore_other_worktrees;
int show_progress;
/*
* If new checkout options are added, skip_merge_working_tree
* should be updated accordingly.
*/
const char *new_branch;
const char *new_branch_force;
@ -471,6 +477,98 @@ static void setup_branch_path(struct branch_info *branch)
branch->path = strbuf_detach(&buf, NULL);
}
/*
* Skip merging the trees, updating the index and working directory if and
* only if we are creating a new branch via "git checkout -b <new_branch>."
*/
static int skip_merge_working_tree(const struct checkout_opts *opts,
const struct branch_info *old_branch_info,
const struct branch_info *new_branch_info)
{
/*
* Do the merge if sparse checkout is on and the user has not opted in
* to the optimized behavior
*/
if (core_apply_sparse_checkout && !checkout_optimize_new_branch)
return 0;
/*
* We must do the merge if we are actually moving to a new commit.
*/
if (!old_branch_info->commit || !new_branch_info->commit ||
oidcmp(&old_branch_info->commit->object.oid, &new_branch_info->commit->object.oid))
return 0;
/*
* opts->patch_mode cannot be used with switching branches so is
* not tested here
*/
/*
* opts->quiet only impacts output so doesn't require a merge
*/
/*
* Honor the explicit request for a three-way merge or to throw away
* local changes
*/
if (opts->merge || opts->force)
return 0;
/*
* --detach is documented as "updating the index and the files in the
* working tree" but this optimization skips those steps so fall through
* to the regular code path.
*/
if (opts->force_detach)
return 0;
/*
* opts->writeout_stage cannot be used with switching branches so is
* not tested here
*/
/*
* Honor the explicit ignore requests
*/
if (!opts->overwrite_ignore || opts->ignore_skipworktree ||
opts->ignore_other_worktrees)
return 0;
/*
* opts->show_progress only impacts output so doesn't require a merge
*/
/*
* If we aren't creating a new branch any changes or updates will
* happen in the existing branch. Since that could only be updating
* the index and working directory, we don't want to skip those steps
* or we've defeated any purpose in running the command.
*/
if (!opts->new_branch)
return 0;
/*
* new_branch_force is defined to "create/reset and checkout a branch"
* so needs to go through the merge to do the reset
*/
if (opts->new_branch_force)
return 0;
/*
* A new orphaned branch requrires the index and the working tree to be
* adjusted to <start_point>
*/
if (opts->new_orphan_branch)
return 0;
/*
* Remaining variables are not checkout options but used to track state
*/
return 1;
}
static int merge_working_tree(const struct checkout_opts *opts,
struct branch_info *old_branch_info,
struct branch_info *new_branch_info,
@ -845,10 +943,19 @@ static int switch_branches(const struct checkout_opts *opts,
parse_commit_or_die(new_branch_info->commit);
}
ret = merge_working_tree(opts, &old_branch_info, new_branch_info, &writeout_error);
if (ret) {
free(path_to_free);
return ret;
/* optimize the "checkout -b <new_branch> path */
if (skip_merge_working_tree(opts, &old_branch_info, new_branch_info)) {
if (!checkout_optimize_new_branch && !opts->quiet) {
if (read_cache_preload(NULL) < 0)
return error(_("index file corrupt"));
show_local_changes(&new_branch_info->commit->object, &opts->diff_options);
}
} else {
ret = merge_working_tree(opts, &old_branch_info, new_branch_info, &writeout_error);
if (ret) {
free(path_to_free);
return ret;
}
}
if (!opts->quiet && !old_branch_info.path && old_branch_info.commit && new_branch_info->commit != old_branch_info.commit)
@ -863,6 +970,11 @@ static int switch_branches(const struct checkout_opts *opts,
static int git_checkout_config(const char *var, const char *value, void *cb)
{
if (!strcmp(var, "checkout.optimizenewbranch")) {
checkout_optimize_new_branch = git_config_bool(var, value);
return 0;
}
if (!strcmp(var, "diff.ignoresubmodules")) {
struct checkout_opts *opts = cb;
handle_ignore_submodules_arg(&opts->diff_options, value);

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@ -31,6 +31,20 @@ test_expect_success 'perform sparse checkout of master' '
test_path_is_file c
'
test_expect_success 'checkout -b checkout.optimizeNewBranch interaction' '
cp .git/info/sparse-checkout .git/info/sparse-checkout.bak &&
test_when_finished "
mv -f .git/info/sparse-checkout.bak .git/info/sparse-checkout
git checkout master
" &&
echo "/b" >>.git/info/sparse-checkout &&
test "$(git ls-files -t b)" = "S b" &&
git -c checkout.optimizeNewBranch=true checkout -b fast &&
test "$(git ls-files -t b)" = "S b" &&
git checkout -b slow &&
test "$(git ls-files -t b)" = "H b"
'
test_expect_success 'merge feature branch into sparse checkout of master' '
git merge feature &&
test_path_is_file a &&