[PATCH 15/16] checkout: add new options to support narrow checkout

["Nguyễn Thái Ngọc Duy" <pclouds@gmail.com>]

These options include:

 --full: return to full checkout (default)
 --path: narrow checkout to some areas according to given spec
 --add-path/--remove-path: adjust current narrow checkout

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
---
 Documentation/git-checkout.txt |   68 +++++++++++++++++++++++++++++++++-
 builtin-checkout.c             |   44 ++++++++++++++++++++++
 t/t2011-checkout-narrow.sh     |   80 ++++++++++++++++++++++++++++++++++++++++
 3 files changed, 190 insertions(+), 2 deletions(-)
 create mode 100755 t/t2011-checkout-narrow.sh

diff --git a/Documentation/git-checkout.txt b/Documentation/git-checkout.txt
index 82e154d..2ae483b 100644
--- a/Documentation/git-checkout.txt
+++ b/Documentation/git-checkout.txt
@@ -8,8 +8,10 @@ git-checkout - Checkout a branch or paths to the working tree
 SYNOPSIS
 --------
 [verse]
-'git checkout' [-q] [-f] [--track | --no-track] [-b <new_branch> [-l]] [-m] [<branch>]
-'git checkout' [-f|--ours|--theirs|-m|--conflict=<style>] [<tree-ish>] [--] <paths>...
+'git checkout' [-q] [-f] [--track | --no-track] [-b <new_branch> [-l]] [-m]
+	  [<narrow options>] [<branch>]
+'git checkout' [-f|--ours|--theirs|-m|--conflict=<style>] [<tree-ish>]
+	  [<narrow options>] [--] <paths>...
 
 DESCRIPTION
 -----------
@@ -34,6 +36,10 @@ used to specify a specific tree-ish (i.e. commit, tag or tree)
 to update the index for the given paths before updating the
 working tree.
 
+<narrow options> include --full, --path, --add-path and --remove-path.
+The last three require narrow spec. Please refer to "narrow checkout"
+section to have more information about this mode.
+
 The index may contain unmerged entries after a failed merge.  By
 default, if you try to check out such an entry from the index, the
 checkout operation will fail and nothing will be checked out.
@@ -108,6 +114,22 @@ exlicitly give a name with '-b' in such a case.
 	However, with this option, a three-way merge between the current
 	branch, your working tree contents, and the new branch
 	is done, and you will be on the new branch.
+
+--full::
+	Quit narrow checkout mode. Return to full checkout.
+
+--path=<narrow_spec>::
+	Re-apply new narrow spec on current working directory to
+	form new checkout area.
+
+--add-path=<narrow_spec>::
+	Checkout more areas specified by narrow spec to current
+	checkout area.
+
+--remove-path=<narrow_spec>::
+	Narrow checkout area by removing files specified by narrow spec
+	from current checkout area. This operation will fail if there
+	is unmerged or modified files in the removing areas.
 +
 When a merge conflict happens, the index entries for conflicting
 paths are left unmerged, and you need to resolve the conflicts
@@ -171,6 +193,48 @@ the reflog for HEAD where you were, e.g.
 $ git log -g -2 HEAD
 ------------
 
+Narrow checkout
+---------------
+
+Normally when you do checkout a branch, your working directory
+will be fully populated. In some situations, you just need to
+work on certain files, no full checkout is required. Narrow
+checkout is a mode that limits checkout area according to your
+rules.
+
+Because narrow checkout uses new index format, it will be
+incompatible with git prior to 1.6.0. In order to make your
+working directory work with those versions, you can use `git
+checkout --full` to return to normal mode (and compatible index
+format).
+
+Narrow works by applying your rules to the index, marking which
+file you need and which file you need not. Modified/Unmerged
+files cannot be marked unneeded. Unnecessary files will be
+removed from working directory.  Note that after this step,
+removed files can still be added to working directory when they
+are needed by any git command. For example, when you have a merge
+conflict, conflicted files will be checked out on working
+directory and will no longer be marked "unneeded".
+
+New files after merges will always be "needed". You can also
+apply rules when switching branches to avoid unwanted new files.
+
+Files that are marked "no-checkout" will be treated like entries
+with "assume-unchanged bit" (see linkgit:git-update-index[1]). In
+short, Git will never look for those files in working directory
+no matter whether they exist in working directory.
+
+You can apply your rules at once with --path option, or do it
+incrementally with --add-path and --remove-path.
+
+Narrow spec will be used to specify how you want to narrow your
+checkout. It is a list of pathspecs separated by colons. Each
+patchspec specifies what files should be checked out on working
+directory. Pathspec can contain wildcards and is relative to
+current working directory. Usually asterisk (*) does not match
+slashes. If a pathspec is prefixed by a plus sign (+), then
+any asterisk will match anything, even slashes.
 
 EXAMPLES
 --------
diff --git a/builtin-checkout.c b/builtin-checkout.c
index c7b0aad..b6bc3c5 100644
--- a/builtin-checkout.c
+++ b/builtin-checkout.c
@@ -33,6 +33,12 @@ struct checkout_opts {
 	const char *new_branch;
 	int new_branch_log;
 	enum branch_track track;
+
+	const char *prefix;
+	char *new_path;
+	char *add_path;
+	char *remove_path;
+	int no_narrow_checkout;
 };
 
 static int post_checkout_hook(struct commit *old, struct commit *new,
@@ -412,6 +418,24 @@ static int merge_working_tree(struct checkout_opts *opts,
 		tree = parse_tree_indirect(new->commit->object.sha1);
 		init_tree_desc(&trees[1], tree->buffer, tree->size);
 
+		topts.narrow_prefix = opts->prefix;
+		if (opts->no_narrow_checkout) {
+			/* leave narrow_spec NULL */
+			topts.new_narrow_path = 1;
+		}
+		else if (opts->new_path) {
+			topts.narrow_spec = opts->new_path;
+			topts.new_narrow_path = 1;
+		}
+		else if (opts->add_path) {
+			topts.narrow_spec = opts->add_path;
+			topts.add_narrow_path = 1;
+		}
+		else if (opts->remove_path) {
+			topts.narrow_spec = opts->remove_path;
+			topts.remove_narrow_path = 1;
+		}
+
 		ret = unpack_trees(2, trees, &topts);
 		if (ret == -1) {
 			/*
@@ -600,6 +624,10 @@ int cmd_checkout(int argc, const char **argv, const char *prefix)
 		OPT_BOOLEAN('m', "merge", &opts.merge, "merge"),
 		OPT_STRING(0, "conflict", &conflict_style, "style",
 			   "conflict style (merge or diff3)"),
+		OPT_BOOLEAN(0, "full", &opts.no_narrow_checkout, "quit sparse checkout"),
+		OPT_STRING(0, "path", &opts.new_path, "prefixes", "apply new narrow checkout path"),
+		OPT_STRING(0, "add-path", &opts.add_path, "prefixes", "add more checkout area"),
+		OPT_STRING(0, "remove-path", &opts.remove_path, "prefixes", "narrow checkout area"),
 		OPT_END(),
 	};
 	int has_dash_dash;
@@ -610,6 +638,7 @@ int cmd_checkout(int argc, const char **argv, const char *prefix)
 	git_config(git_checkout_config, NULL);
 
 	opts.track = BRANCH_TRACK_UNSPECIFIED;
+	opts.prefix = prefix;
 
 	argc = parse_options(argc, argv, options, checkout_usage,
 			     PARSE_OPT_KEEP_DASHDASH);
@@ -639,6 +668,18 @@ int cmd_checkout(int argc, const char **argv, const char *prefix)
 	if (!opts.new_branch && (opts.track != git_branch_track))
 		die("git checkout: --track and --no-track require -b");
 
+	if (((opts.no_narrow_checkout ? 1 : 0) +
+	     (opts.new_path ? 1 : 0) +
+	     (opts.add_path ? 1 : 0) +
+	     (opts.remove_path ? 1 : 0)) > 1)
+		die("git checkout: --path, --full, --add-path and --remove-path are incompatible");
+
+	if (opts.new_branch && (opts.add_path || opts.remove_path))
+		die("git checkout: --add-path and --remove-path should only be used on current branch");
+
+	if (opts.new_branch && opts.no_narrow_checkout)
+		die("git checkout: switching branch with --full does not make sense");
+
 	if (opts.force && opts.merge)
 		die("git checkout: -f and -m are incompatible");
 
@@ -732,6 +773,9 @@ no_reference:
 		if (1 < !!opts.writeout_stage + !!opts.force + !!opts.merge)
 			die("git checkout: --ours/--theirs, --force and --merge are incompatible when\nchecking out of the index.");
 
+		if (opts.no_narrow_checkout || opts.new_path || opts.add_path || opts.remove_path)
+			die("git checkout: updating paths is incompatible with setting sparse checkout");
+
 		return checkout_paths(source_tree, pathspec, &opts);
 	}
 
diff --git a/t/t2011-checkout-narrow.sh b/t/t2011-checkout-narrow.sh
new file mode 100755
index 0000000..77b99e1
--- /dev/null
+++ b/t/t2011-checkout-narrow.sh
@@ -0,0 +1,80 @@
+#!/bin/sh
+
+test_description='narrow checkout'
+
+. ./test-lib.sh
+
+test_expect_success setup '
+	mkdir work1 work2 work3
+	touch one two three
+	touch work1/one work2/two work3/three
+	git add one work1/one
+	git commit -m work1
+	git add two work2/two
+	git commit -m work2
+	git add three work3/three
+	git commit -m work3
+'
+
+test_expect_success '--full on no-narrow checkout' '
+	git checkout --full
+'
+
+test_expect_success '--full and --path incompatible' '
+	test_must_fail git checkout --full --path=work1
+'
+
+test_expect_success 'limit worktree to work1 and work2' '
+	git checkout --path="work1/*:work2/*" &&
+	test -f work1/one &&
+	test -f work2/two &&
+	! test -f work3/three
+'
+
+test_expect_success 'update worktree to work2 and work3' '
+	git checkout --path="work2/*:work3/*" &&
+	! test -f work1/one &&
+	test -f work2/two &&
+	test -f work3/three
+'
+
+test_expect_success 'update narrow prefix with modification' '
+	echo modified >> work2/two &&
+	git checkout --path="work1/*:work2/*" &&
+	test -f work1/one &&
+	test -f work2/two &&
+	! test -f work3/three &&
+	grep -q modified work2/two
+'
+
+test_expect_success 'update narrow should not lose modification' '
+	! git checkout --path="work1/*:work3/*" &&
+	test -f work1/one &&
+	test -f work2/two &&
+	! test -f work3/three &&
+	grep -q modified work2/two
+'
+
+test_expect_success 'widen checkout area' '
+	git checkout --add-path="work3/*" &&
+	test -f work1/one &&
+	test -f work2/two &&
+	test -f work3/three
+'
+
+test_expect_success 'narrow checkout area' '
+	git checkout --remove-path="work3/*" &&
+	test -f work1/one &&
+	test -f work2/two &&
+	! test -f work3/three
+'
+
+test_expect_success 'exit narrow checkout' '
+	git checkout --full &&
+	test -f work1/one &&
+	test -f work2/two &&
+	test -f work3/three &&
+	test one
+'
+
+test_done
-- 
1.6.0.96.g2fad1.dirty