[PATCH 2/4] reset: accept "git reset <tree> <path>"

[Jonathan Nieder <jrnieder@gmail.com>]

The <rev> argument in

	git reset --hard <rev>
	git reset --soft <rev>

needs to be a commit to be sensible.  But in

	git reset <rev> -- <path> <path> ...

using other trees can be useful.

For example, to apply changes from a branch that has the current
branch merged as a subtree:

	git reset master:gitk-git -- .

Signed-off-by: Jonathan Nieder <jrnieder@gmail.com>
---
 builtin/reset.c  |   11 ++++++-----
 t/t7102-reset.sh |   31 +++++++++++++++++++++++++++++++
 2 files changed, 37 insertions(+), 5 deletions(-)

diff --git a/builtin/reset.c b/builtin/reset.c
index a52e6f8..2375472 100644
--- a/builtin/reset.c
+++ b/builtin/reset.c
@@ -306,15 +306,10 @@ int cmd_reset(int argc, const char **argv, const char *prefix)
 	}
 
 	if (get_sha1(rev, sha1))
 		die("Failed to resolve '%s' as a valid ref.", rev);
 
-	commit = lookup_commit_reference(sha1);
-	if (!commit)
-		die("Could not parse object '%s'.", rev);
-	hashcpy(sha1, commit->object.sha1);
-
 	/* git reset tree [--] paths... can be used to
 	 * load chosen paths from the tree into the index without
 	 * affecting the working tree nor HEAD. */
 	if (i < argc) {
 		if (reset_type == MIXED)
@@ -323,10 +318,16 @@ int cmd_reset(int argc, const char **argv, const char *prefix)
 			die("Cannot do %s reset with paths.",
 					reset_type_names[reset_type]);
 		return read_from_tree(prefix, argv + i, sha1,
 				quiet ? REFRESH_QUIET : REFRESH_IN_PORCELAIN);
 	}
+
+	commit = lookup_commit_reference(sha1);
+	if (!commit)
+		die("Could not parse object '%s'.", rev);
+	hashcpy(sha1, commit->object.sha1);
+
 	if (reset_type == NONE)
 		reset_type = MIXED; /* by default */
 
 	if (reset_type != SOFT && reset_type != MIXED)
 		setup_work_tree();
diff --git a/t/t7102-reset.sh b/t/t7102-reset.sh
index b8cf260..3e95da3 100755
--- a/t/t7102-reset.sh
+++ b/t/t7102-reset.sh
@@ -7,10 +7,18 @@ test_description='git reset
 
 Documented tests for git reset'
 
 . ./test-lib.sh
 
+test_exit_code () {
+	echo $1 >expect.code &&
+	shift &&
+	"$@"
+	echo $? >actual.code &&
+	test_cmp expect.code actual.code
+}
+
 test_expect_success 'creating initial files and commits' '
 	test_tick &&
 	echo "1st file" >first &&
 	git add first &&
 	git commit -m "create 1st file" &&
@@ -409,17 +417,40 @@ test_expect_success 'test resetting the index at give paths' '
 	test_must_fail git diff-index --cached --exit-code "$T" &&
 	test "$T" != "$U"
 
 '
 
+test_expect_success 'reset modified path from tree' '
+	echo hello >other &&
+	git reset --hard &&
+	git add other &&
+	T=$(git write-tree) &&
+	git rm -f other &&
+	test_exit_code 1 git reset $T other &&
+	git diff-index --cached --exit-code "$T"
+'
+
+test_expect_success 'try to reset from blob' '
+	git reset --hard &&
+	B=$(git rev-parse --verify HEAD:file1) &&
+	test_exit_code 128 git reset $B -- .
+'
+
 test_expect_success 'resetting an unmodified path is a no-op' '
 	git reset --hard &&
 	git reset -- file1 &&
 	git diff-files --exit-code &&
 	git diff-index --cached --exit-code HEAD
 '
 
+test_expect_success 'reset unmodified path from tree' '
+	git reset --hard &&
+	git reset HEAD^{tree} -- file1 &&
+	git diff-files --exit-code &&
+	git diff-index --cached --exit-code HEAD
+'
+
 cat > expect << EOF
 Unstaged changes after reset:
 M	file2
 EOF
 
-- 
1.7.2.3