Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
---
 .gitignore                          |    1 +
 Documentation/git-checkout.txt      |    3 +-
 Documentation/git-update-index.txt  |   13 ++++++++++++
 Makefile                            |    2 +-
 builtin-update-index.c              |   16 ++++++++++++++-
 t/t2104-update-index-no-checkout.sh |   36 +++++++++++++++++++++++++++++++++++
 test-index-version.c                |   14 +++++++++++++
 7 files changed, 82 insertions(+), 3 deletions(-)
 create mode 100755 t/t2104-update-index-no-checkout.sh
 create mode 100644 test-index-version.c

diff --git a/.gitignore b/.gitignore
index bbaf9de..0c35577 100644
--- a/.gitignore
+++ b/.gitignore
@@ -147,6 +147,7 @@ test-date
 test-delta
 test-dump-cache-tree
 test-genrandom
+test-index-version
 test-match-trees
 test-parse-options
 test-path-utils
diff --git a/Documentation/git-checkout.txt b/Documentation/git-checkout.txt
index 4bd9eba..2b344e1 100644
--- a/Documentation/git-checkout.txt
+++ b/Documentation/git-checkout.txt
@@ -196,7 +196,8 @@ to index, it will be marked "checkout" unless sparse patterns are
 applied.  Unmerged files are always "checkout". When you checkout new
 files using "git checkout <file>" they will be automatically marked
 "checkout". Other commands such as "git apply" can also checkout new
-files if they are needed.
+files if they are needed. linkgit:git-update-index[1] can be used to
+update "checkout/no-checkout" status in index.
 
 "No-checkout" status is very similar to "assume-unchanged bit"
 (see linkgit:git-update-index[1]). The main difference between them
diff --git a/Documentation/git-update-index.txt b/Documentation/git-update-index.txt
index 1d9d81a..ec03e05 100644
--- a/Documentation/git-update-index.txt
+++ b/Documentation/git-update-index.txt
@@ -15,6 +15,7 @@ SYNOPSIS
 	     [--cacheinfo <mode> <object> <file>]\*
 	     [--chmod=(+|-)x]
 	     [--assume-unchanged | --no-assume-unchanged]
+	     [--checkout | --no-checkout]
 	     [--ignore-submodules]
 	     [--really-refresh] [--unresolve] [--again | -g]
 	     [--info-only] [--index-info]
@@ -99,6 +100,18 @@ in the index e.g. when merging in a commit;
 thus, in case the assumed-untracked file is changed upstream,
 you will need to handle the situation manually.
 
+--checkout::
+--no-checkout::
+	When one of these flags is specified, the object name recorded
+	for the paths are not updated. Instead, these options
+	set and unset the "no-checkout" bit for the paths. This
+	bit is used for marking files for sparse checkout. If
+	a path is marked "no-checkout", then it should not be
+	checked out unless requested by user or needed for a git
+	command to function.
+	See linkgit:git-checkout[1] for more information about
+	sparse checkout.
+
 -g::
 --again::
 	Runs 'git-update-index' itself on the paths whose index
diff --git a/Makefile b/Makefile
index e0c03c3..edb33cb 100644
--- a/Makefile
+++ b/Makefile
@@ -1327,7 +1327,7 @@ endif
 
 ### Testing rules
 
-TEST_PROGRAMS = test-chmtime$X test-genrandom$X test-date$X test-delta$X test-sha1$X test-match-trees$X test-parse-options$X test-path-utils$X
+TEST_PROGRAMS = test-chmtime$X test-genrandom$X test-date$X test-delta$X test-sha1$X test-match-trees$X test-parse-options$X test-path-utils$X test-index-version$X
 
 all:: $(TEST_PROGRAMS)
 
diff --git a/builtin-update-index.c b/builtin-update-index.c
index ae94739..7514aff 100644
--- a/builtin-update-index.c
+++ b/builtin-update-index.c
@@ -24,6 +24,7 @@ static int info_only;
 static int force_remove;
 static int verbose;
 static int mark_valid_only;
+static int mark_no_checkout_only;
 #define MARK_FLAG 1
 #define UNMARK_FLAG 2
 
@@ -276,6 +277,11 @@ static void update_one(const char *path, const char *prefix, int prefix_length)
 			die("Unable to mark file %s", path);
 		goto free_return;
 	}
+	if (mark_no_checkout_only) {
+		if (mark_ce_flags(p, CE_NO_CHECKOUT, mark_no_checkout_only == MARK_FLAG))
+			die("Unable to mark file %s", path);
+		goto free_return;
+	}
 
 	if (force_remove) {
 		if (remove_file_from_cache(p))
@@ -386,7 +392,7 @@ static void read_index_info(int line_termination)
 }
 
 static const char update_index_usage[] =
-"git update-index [-q] [--add] [--replace] [--remove] [--unmerged] [--refresh] [--really-refresh] [--cacheinfo] [--chmod=(+|-)x] [--assume-unchanged] [--info-only] [--force-remove] [--stdin] [--index-info] [--unresolve] [--again | -g] [--ignore-missing] [-z] [--verbose] [--] <file>...";
+"git update-index [-q] [--add] [--replace] [--remove] [--unmerged] [--refresh] [--really-refresh] [--cacheinfo] [--chmod=(+|-)x] [--assume-unchanged] [--checkout|--no-checkout] [--info-only] [--force-remove] [--stdin] [--index-info] [--unresolve] [--again | -g] [--ignore-missing] [-z] [--verbose] [--] <file>...";
 
 static unsigned char head_sha1[20];
 static unsigned char merge_head_sha1[20];
@@ -652,6 +658,14 @@ int cmd_update_index(int argc, const char **argv, const char *prefix)
 				mark_valid_only = UNMARK_FLAG;
 				continue;
 			}
+			if (!strcmp(path, "--checkout")) {
+				mark_no_checkout_only = UNMARK_FLAG;
+				continue;
+			}
+			if (!strcmp(path, "--no-checkout")) {
+				mark_no_checkout_only = MARK_FLAG;
+				continue;
+			}
 			if (!strcmp(path, "--info-only")) {
 				info_only = 1;
 				continue;
diff --git a/t/t2104-update-index-no-checkout.sh b/t/t2104-update-index-no-checkout.sh
new file mode 100755
index 0000000..be9f913
--- /dev/null
+++ b/t/t2104-update-index-no-checkout.sh
@@ -0,0 +1,36 @@
+#!/bin/sh
+#
+# Copyright (c) 2008 Nguyễn Thái Ngọc Duy
+#
+
+test_description='git update-index no-checkout bits (a.k.a sparse checkout)'
+
+. ./test-lib.sh
+
+test_expect_success 'setup' '
+	mkdir sub &&
+	touch 1 2 sub/1 sub/2 &&
+	git add 1 2 sub/1 sub/2
+'
+
+test_expect_success 'index is at version 2' '
+	test "$(test-index-version < .git/index)" = 2
+'
+
+test_expect_success 'update-index --no-checkout' '
+	git update-index --no-checkout 1 sub/1 &&
+	test -z "$(git ls-files --sparse|grep 1)"'
+
+test_expect_success 'index is at version 3 after having some no-checkout entries' '
+	test "$(test-index-version < .git/index)" = 3
+'
+
+test_expect_success 'update-index --checkout' '
+	git update-index --checkout 1 sub/1 &&
+	test "$(git ls-files)" = "$(git ls-files --sparse)"'
+
+test_expect_success 'index version is back to 2 when there is no no-checkout entry' '
+	test "$(test-index-version < .git/index)" = 2
+'
+
+test_done
diff --git a/test-index-version.c b/test-index-version.c
new file mode 100644
index 0000000..bfaad9e
--- /dev/null
+++ b/test-index-version.c
@@ -0,0 +1,14 @@
+#include "cache.h"
+
+int main(int argc, const char **argv)
+{
+	struct cache_header hdr;
+	int version;
+
+	memset(&hdr,0,sizeof(hdr));
+	if (read(0, &hdr, sizeof(hdr)) != sizeof(hdr))
+		return 0;
+	version = ntohl(hdr.hdr_version);
+	printf("%d\n", version);
+	return 0;
+}
-- 
1.6.0.2.488.gf604a

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