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>
Ben Peart committed
Aug 16, 2018 at 18:27 UTC
fa655d8411cc2d7ffcf898e53a1493c737d7de68
3 files changed
+138
-4
Documentation/config.txt
+8
@@ -1101,6 +1101,14 @@ browser.<tool>.path::
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browse HTML help (see `-w` option in linkgit:git-help[1]) or a
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working repository in gitweb (see linkgit:git-instaweb[1]).
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+checkout.optimizeNewBranch
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+ Optimizes the performance of "git checkout -b <new_branch>" when
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+ using sparse-checkout. When set to true, git will not update the
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+ repo based on the current sparse-checkout settings. This means it
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+ will not update the skip-worktree bit in the index nor add/remove
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+ files in the working directory to reflect the current sparse checkout
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+ settings nor will it show the local changes.
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+
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clean.requireForce::
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A boolean to make git-clean do nothing unless given -f,
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-i or -n. Defaults to true.
builtin/checkout.c
+116
-4
@@ -24,6 +24,8 @@
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#include "submodule-config.h"
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#include "submodule.h"
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+static int checkout_optimize_new_branch;
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+
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static const char * const checkout_usage[] = {
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N_("git checkout [<options>] <branch>"),
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N_("git checkout [<options>] [<branch>] -- <file>..."),
@@ -41,6 +43,10 @@ struct checkout_opts {
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int ignore_skipworktree;
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int ignore_other_worktrees;
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int show_progress;
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+ /*
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+ * If new checkout options are added, skip_merge_working_tree
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+ * should be updated accordingly.
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+ */
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const char *new_branch;
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const char *new_branch_force;
@@ -471,6 +477,98 @@ static void setup_branch_path(struct branch_info *branch)
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branch->path = strbuf_detach(&buf, NULL);
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}
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+/*
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+ * Skip merging the trees, updating the index and working directory if and
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+ * only if we are creating a new branch via "git checkout -b <new_branch>."
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+ */
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+static int skip_merge_working_tree(const struct checkout_opts *opts,
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+ const struct branch_info *old_branch_info,
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+ const struct branch_info *new_branch_info)
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+{
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+ /*
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+ * Do the merge if sparse checkout is on and the user has not opted in
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+ * to the optimized behavior
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+ */
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+ if (core_apply_sparse_checkout && !checkout_optimize_new_branch)
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+ return 0;
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+
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+ /*
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+ * We must do the merge if we are actually moving to a new commit.
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+ */
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+ if (!old_branch_info->commit || !new_branch_info->commit ||
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+ oidcmp(&old_branch_info->commit->object.oid, &new_branch_info->commit->object.oid))
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+ return 0;
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+
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+ /*
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+ * opts->patch_mode cannot be used with switching branches so is
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+ * not tested here
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+ */
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+
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+ /*
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+ * opts->quiet only impacts output so doesn't require a merge
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+ */
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+
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+ /*
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+ * Honor the explicit request for a three-way merge or to throw away
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+ * local changes
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+ */
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+ if (opts->merge || opts->force)
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+ return 0;
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+
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+ /*
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+ * --detach is documented as "updating the index and the files in the
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+ * working tree" but this optimization skips those steps so fall through
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+ * to the regular code path.
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+ */
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+ if (opts->force_detach)
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+ return 0;
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+
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+ /*
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+ * opts->writeout_stage cannot be used with switching branches so is
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+ * not tested here
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+ */
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+
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+ /*
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+ * Honor the explicit ignore requests
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+ */
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+ if (!opts->overwrite_ignore || opts->ignore_skipworktree ||
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+ opts->ignore_other_worktrees)
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+ return 0;
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+
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+ /*
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+ * opts->show_progress only impacts output so doesn't require a merge
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+ */
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+
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+ /*
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+ * If we aren't creating a new branch any changes or updates will
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+ * happen in the existing branch. Since that could only be updating
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+ * the index and working directory, we don't want to skip those steps
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+ * or we've defeated any purpose in running the command.
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+ */
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+ if (!opts->new_branch)
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+ return 0;
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+
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+ /*
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+ * new_branch_force is defined to "create/reset and checkout a branch"
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+ * so needs to go through the merge to do the reset
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+ */
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+ if (opts->new_branch_force)
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+ return 0;
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+
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+ /*
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+ * A new orphaned branch requrires the index and the working tree to be
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+ * adjusted to <start_point>
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+ */
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+ if (opts->new_orphan_branch)
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+ return 0;
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+
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+ /*
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+ * Remaining variables are not checkout options but used to track state
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+ */
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+
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+ return 1;
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+}
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+
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static int merge_working_tree(const struct checkout_opts *opts,
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struct branch_info *old_branch_info,
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struct branch_info *new_branch_info,
@@ -845,10 +943,19 @@ static int switch_branches(const struct checkout_opts *opts,
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parse_commit_or_die(new_branch_info->commit);
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}
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- ret = merge_working_tree(opts, &old_branch_info, new_branch_info, &writeout_error);
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- if (ret) {
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- free(path_to_free);
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- return ret;
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+ /* optimize the "checkout -b <new_branch> path */
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+ if (skip_merge_working_tree(opts, &old_branch_info, new_branch_info)) {
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+ if (!checkout_optimize_new_branch && !opts->quiet) {
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+ if (read_cache_preload(NULL) < 0)
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+ return error(_("index file corrupt"));
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+ show_local_changes(&new_branch_info->commit->object, &opts->diff_options);
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+ }
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+ } else {
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+ ret = merge_working_tree(opts, &old_branch_info, new_branch_info, &writeout_error);
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+ if (ret) {
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+ free(path_to_free);
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+ return ret;
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+ }
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}
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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,
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static int git_checkout_config(const char *var, const char *value, void *cb)
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{
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+ if (!strcmp(var, "checkout.optimizenewbranch")) {
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+ checkout_optimize_new_branch = git_config_bool(var, value);
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+ return 0;
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+ }
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+
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if (!strcmp(var, "diff.ignoresubmodules")) {
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struct checkout_opts *opts = cb;
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handle_ignore_submodules_arg(&opts->diff_options, value);
t/t1090-sparse-checkout-scope.sh
+14
@@ -31,6 +31,20 @@ test_expect_success 'perform sparse checkout of master' '
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test_path_is_file c
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'
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+test_expect_success 'checkout -b checkout.optimizeNewBranch interaction' '
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+ cp .git/info/sparse-checkout .git/info/sparse-checkout.bak &&
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+ test_when_finished "
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+ mv -f .git/info/sparse-checkout.bak .git/info/sparse-checkout
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+ git checkout master
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+ " &&
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+ echo "/b" >>.git/info/sparse-checkout &&
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+ test "$(git ls-files -t b)" = "S b" &&
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+ git -c checkout.optimizeNewBranch=true checkout -b fast &&
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+ test "$(git ls-files -t b)" = "S b" &&
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+ git checkout -b slow &&
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+ test "$(git ls-files -t b)" = "H b"
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+'
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+
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test_expect_success 'merge feature branch into sparse checkout of master' '
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git merge feature &&
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test_path_is_file a &&