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Nguyễn Thái Ngọc Duy  committed a2b7a3b

diff: support --cached on unborn branches

"git diff --cached" (without revision) used to mean "git diff --cached
HEAD" (i.e. the user was too lazy to type HEAD). This "correctly"
failed when there was no commit yet. But was that correctness useful?

This patch changes the definition of what particular command means.
It is a request to show what _would_ be committed without further "git
add". The internal implementation is the same "git diff --cached HEAD"
when HEAD exists, but when there is no commit yet, it compares the index
with an empty tree object to achieve the desired result.

Signed-off-by: Junio C Hamano <gitster@pobox.com>
Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

  • Participants
  • Parent commits 2e9c878

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Files changed (5)

File Documentation/git-diff.txt

 	commit relative to the named <commit>.  Typically you
 	would want comparison with the latest commit, so if you
 	do not give <commit>, it defaults to HEAD.
+	If HEAD does not exist (e.g. unborned branches) and
+	<commit> is not given, it shows all staged changes.
 	--staged is a synonym of --cached.
 
 'git diff' [--options] <commit> [--] [<path>...]::

File builtin/diff.c

 			else if (!strcmp(arg, "--cached") ||
 				 !strcmp(arg, "--staged")) {
 				add_head_to_pending(&rev);
-				if (!rev.pending.nr)
-					die("No HEAD commit to compare with (yet)");
+				if (!rev.pending.nr) {
+					struct tree *tree;
+					tree = lookup_tree((const unsigned char*)EMPTY_TREE_SHA1_BIN);
+					add_pending_object(&rev, &tree->object, "HEAD");
+				}
 				break;
 			}
 		}

File t/t4013-diff-various.sh

 	test_must_fail git log -S
 '
 
+test_expect_success 'diff --cached on unborn branch' '
+	echo ref: refs/heads/unborn >.git/HEAD &&
+	git diff --cached >result &&
+	test_cmp "$TEST_DIRECTORY/t4013/diff.diff_--cached" result
+'
+
+test_expect_success 'diff --cached -- file on unborn branch' '
+	git diff --cached -- file0 >result &&
+	test_cmp "$TEST_DIRECTORY/t4013/diff.diff_--cached_--_file0" result
+'
+
 test_done

File t/t4013/diff.diff_--cached

+diff --git a/dir/sub b/dir/sub
+new file mode 100644
+index 0000000..992913c
+--- /dev/null
++++ b/dir/sub
+@@ -0,0 +1,8 @@
++A
++B
++C
++D
++E
++F
++1
++2
+diff --git a/file0 b/file0
+new file mode 100644
+index 0000000..10a8a9f
+--- /dev/null
++++ b/file0
+@@ -0,0 +1,9 @@
++1
++2
++3
++4
++5
++6
++A
++B
++C
+diff --git a/file1 b/file1
+new file mode 100644
+index 0000000..b1e6722
+--- /dev/null
++++ b/file1
+@@ -0,0 +1,3 @@
++A
++B
++C

File t/t4013/diff.diff_--cached_--_file0

+diff --git a/file0 b/file0
+new file mode 100644
+index 0000000..10a8a9f
+--- /dev/null
++++ b/file0
+@@ -0,0 +1,9 @@
++1
++2
++3
++4
++5
++6
++A
++B
++C