Merge branch 'tg/index-v4-format'

* tg/index-v4-format:
  read-cache: add index.version config variable
  test-lib: allow setting the index format version
  introduce GIT_INDEX_VERSION environment variable

Documentation/config.txt

@@ -1607,6 +1607,10 @@ imap::
 	The configuration variables in the 'imap' section are described
 	in linkgit:git-imap-send[1].
 
+index.version::
+	Specify the version with which new index files should be
+	initialized.  This does not affect existing repositories.
+
 init.templatedir::
 	Specify the directory from which templates will be copied.
 	(See the "TEMPLATE DIRECTORY" section of linkgit:git-init[1].)

Documentation/git.txt

@@ -720,6 +720,11 @@ Git so take care if using Cogito etc.
 	index file. If not specified, the default of `$GIT_DIR/index`
 	is used.
 
+'GIT_INDEX_VERSION'::
+	This environment variable allows the specification of an index
+	version for new repositories.  It won't affect existing index
+	files.  By default index file version [23] is used.
+
 'GIT_OBJECT_DIRECTORY'::
 	If the object storage directory is specified via this
 	environment variable then the sha1 directories are created

Makefile

@@ -334,6 +334,10 @@ all::
 # Define DEFAULT_HELP_FORMAT to "man", "info" or "html"
 # (defaults to "man") if you want to have a different default when
 # "git help" is called without a parameter specifying the format.
+#
+# Define TEST_GIT_INDEX_VERSION to 2, 3 or 4 to run the test suite
+# with a different indexfile format version.  If it isn't set the index
+# file format used is index-v[23].
 
 GIT-VERSION-FILE: FORCE
 	@$(SHELL_PATH) ./GIT-VERSION-GEN
@@ -2212,6 +2216,9 @@ endif
 ifdef GIT_PERF_MAKE_OPTS
 	@echo GIT_PERF_MAKE_OPTS=\''$(subst ','\'',$(subst ','\'',$(GIT_PERF_MAKE_OPTS)))'\' >>$@
 endif
+ifdef TEST_GIT_INDEX_VERSION
+	@echo TEST_GIT_INDEX_VERSION=\''$(subst ','\'',$(subst ','\'',$(TEST_GIT_INDEX_VERSION)))'\' >>$@
+endif
 
 ### Detect Python interpreter path changes
 ifndef NO_PYTHON

read-cache.c

@@ -1220,6 +1220,42 @@ static struct cache_entry *refresh_cache_entry(struct cache_entry *ce,
 
 #define INDEX_FORMAT_DEFAULT 3
 
+static int index_format_config(const char *var, const char *value, void *cb)
+{
+	unsigned int *version = cb;
+	if (!strcmp(var, "index.version")) {
+		*version = git_config_int(var, value);
+		return 0;
+	}
+	return 1;
+}
+
+static unsigned int get_index_format_default(void)
+{
+	char *envversion = getenv("GIT_INDEX_VERSION");
+	char *endp;
+	unsigned int version = INDEX_FORMAT_DEFAULT;
+
+	if (!envversion) {
+		git_config(index_format_config, &version);
+		if (version < INDEX_FORMAT_LB || INDEX_FORMAT_UB < version) {
+			warning(_("index.version set, but the value is invalid.\n"
+				  "Using version %i"), INDEX_FORMAT_DEFAULT);
+			return INDEX_FORMAT_DEFAULT;
+		}
+		return version;
+	}
+
+	version = strtoul(envversion, &endp, 10);
+	if (*endp ||
+	    version < INDEX_FORMAT_LB || INDEX_FORMAT_UB < version) {
+		warning(_("GIT_INDEX_VERSION set, but the value is invalid.\n"
+			  "Using version %i"), INDEX_FORMAT_DEFAULT);
+		version = INDEX_FORMAT_DEFAULT;
+	}
+	return version;
+}
+
 /*
  * dev/ino/uid/gid/size are also just tracked to the low 32 bits
  * Again - this is just a (very strong in practice) heuristic that
@@ -1776,7 +1812,7 @@ int write_index(struct index_state *istate, int newfd)
 	}
 
 	if (!istate->version)
-		istate->version = INDEX_FORMAT_DEFAULT;
+		istate->version = get_index_format_default();
 
 	/* demote version 3 to version 2 when the latter suffices */
 	if (istate->version == 3 || istate->version == 2)

t/t1600-index.sh

@@ -0,0 +1,76 @@
+#!/bin/sh
+
+test_description='index file specific tests'
+
+. ./test-lib.sh
+
+test_expect_success 'setup' '
+	echo 1 >a
+'
+
+test_expect_success 'bogus GIT_INDEX_VERSION issues warning' '
+	(
+		rm -f .git/index &&
+		GIT_INDEX_VERSION=2bogus &&
+		export GIT_INDEX_VERSION &&
+		git add a 2>&1 | sed "s/[0-9]//" >actual.err &&
+		sed -e "s/ Z$/ /" <<-\EOF >expect.err &&
+			warning: GIT_INDEX_VERSION set, but the value is invalid.
+			Using version Z
+		EOF
+		test_i18ncmp expect.err actual.err
+	)
+'
+
+test_expect_success 'out of bounds GIT_INDEX_VERSION issues warning' '
+	(
+		rm -f .git/index &&
+		GIT_INDEX_VERSION=1 &&
+		export GIT_INDEX_VERSION &&
+		git add a 2>&1 | sed "s/[0-9]//" >actual.err &&
+		sed -e "s/ Z$/ /" <<-\EOF >expect.err &&
+			warning: GIT_INDEX_VERSION set, but the value is invalid.
+			Using version Z
+		EOF
+		test_i18ncmp expect.err actual.err
+	)
+'
+
+test_expect_success 'no warning with bogus GIT_INDEX_VERSION and existing index' '
+	(
+		GIT_INDEX_VERSION=1 &&
+		export GIT_INDEX_VERSION &&
+		git add a 2>actual.err &&
+		>expect.err &&
+		test_i18ncmp expect.err actual.err
+	)
+'
+
+test_expect_success 'out of bounds index.version issues warning' '
+	(
+		sane_unset GIT_INDEX_VERSION &&
+		rm -f .git/index &&
+		git config --add index.version 1 &&
+		git add a 2>&1 | sed "s/[0-9]//" >actual.err &&
+		sed -e "s/ Z$/ /" <<-\EOF >expect.err &&
+			warning: index.version set, but the value is invalid.
+			Using version Z
+		EOF
+		test_i18ncmp expect.err actual.err
+	)
+'
+
+test_expect_success 'GIT_INDEX_VERSION takes precedence over config' '
+	(
+		rm -f .git/index &&
+		GIT_INDEX_VERSION=4 &&
+		export GIT_INDEX_VERSION &&
+		git config --add index.version 2 &&
+		git add a 2>&1 &&
+		echo 4 >expect &&
+		test-index-version <.git/index >actual &&
+		test_cmp expect actual
+	)
+'
+
+test_done

t/t2104-update-index-skip-worktree.sh

@@ -7,6 +7,8 @@ test_description='skip-worktree bit test'
 
 . ./test-lib.sh
 
+test_set_index_version 3
+
 cat >expect.full <<EOF
 H 1
 H 2

t/test-lib-functions.sh

@@ -32,6 +32,11 @@ test_set_editor () {
 	export EDITOR
 }
 
+test_set_index_version () {
+    GIT_INDEX_VERSION="$1"
+    export GIT_INDEX_VERSION
+}
+
 test_decode_color () {
 	awk '
 		function name(n) {

t/test-lib.sh

@@ -108,6 +108,12 @@ export GIT_AUTHOR_EMAIL GIT_AUTHOR_NAME
 export GIT_COMMITTER_EMAIL GIT_COMMITTER_NAME
 export EDITOR
 
+if test -n "${TEST_GIT_INDEX_VERSION:+isset}"
+then
+	GIT_INDEX_VERSION="$TEST_GIT_INDEX_VERSION"
+	export GIT_INDEX_VERSION
+fi
+
 # Add libc MALLOC and MALLOC_PERTURB test
 # only if we are not executing the test with valgrind
 if expr " $GIT_TEST_OPTS " : ".* --valgrind " >/dev/null ||