Merge branch 'dl/checkout-p-merge-base'

"git checkout -p A...B [-- <path>]" did not work, even though the
same command without "-p" correctly used the merge-base between
commits A and B.

* dl/checkout-p-merge-base:
  t2016: add a NEEDSWORK about the PERL prerequisite
  add-patch: add NEEDSWORK about comparing commits
  Doc: document "A...B" form for <tree-ish> in checkout and switch
  builtin/checkout: fix `git checkout -p HEAD...` bug

Documentation/git-checkout.txt

@@ -351,6 +351,10 @@ leave out at most one of `A` and `B`, in which case it defaults to `HEAD`.
 <tree-ish>::
 	Tree to checkout from (when paths are given). If not specified,
 	the index will be used.
++
+As a special case, you may use `"A...B"` as a shortcut for the
+merge base of `A` and `B` if there is exactly one merge base. You can
+leave out at most one of `A` and `B`, in which case it defaults to `HEAD`.
 
 \--::
 	Do not interpret any more arguments as options.

Documentation/git-restore.txt

@@ -40,6 +40,10 @@ OPTIONS
 +
 If not specified, the contents are restored from `HEAD` if `--staged` is
 given, otherwise from the index.
++
+As a special case, you may use `"A...B"` as a shortcut for the
+merge base of `A` and `B` if there is exactly one merge base. You can
+leave out at most one of `A` and `B`, in which case it defaults to `HEAD`.
 
 -p::
 --patch::

add-patch.c

@@ -1695,6 +1695,14 @@ int run_add_p(struct repository *r, enum add_p_mode mode,
 	if (mode == ADD_P_STASH)
 		s.mode = &patch_mode_stash;
 	else if (mode == ADD_P_RESET) {
+		/*
+		 * NEEDSWORK: Instead of comparing to the literal "HEAD",
+		 * compare the commit objects instead so that other ways of
+		 * saying the same thing (such as "@") are also handled
+		 * appropriately.
+		 *
+		 * This applies to the cases below too.
+		 */
 		if (!revision || !strcmp(revision, "HEAD"))
 			s.mode = &patch_mode_reset_head;
 		else

builtin/checkout.c

@@ -471,6 +471,19 @@ static int checkout_paths(const struct checkout_opts *opts,
 
 	if (opts->patch_mode) {
 		const char *patch_mode;
+		const char *rev = new_branch_info->name;
+		char rev_oid[GIT_MAX_HEXSZ + 1];
+
+		/*
+		 * Since rev can be in the form of `<a>...<b>` (which is not
+		 * recognized by diff-index), we will always replace the name
+		 * with the hex of the commit (whether it's in `...` form or
+		 * not) for the run_add_interactive() machinery to work
+		 * properly. However, there is special logic for the HEAD case
+		 * so we mustn't replace that.
+		 */
+		if (rev && strcmp(rev, "HEAD"))
+			rev = oid_to_hex_r(rev_oid, &new_branch_info->commit->object.oid);
 
 		if (opts->checkout_index && opts->checkout_worktree)
 			patch_mode = "--patch=checkout";
@@ -481,7 +494,7 @@ static int checkout_paths(const struct checkout_opts *opts,
 		else
 			BUG("either flag must have been set, worktree=%d, index=%d",
 			    opts->checkout_worktree, opts->checkout_index);
-		return run_add_interactive(new_branch_info->name, patch_mode, &opts->pathspec);
+		return run_add_interactive(rev, patch_mode, &opts->pathspec);
 	}
 
 	repo_hold_locked_index(the_repository, &lock_file, LOCK_DIE_ON_ERROR);

git-add--interactive.perl

@@ -1830,6 +1830,13 @@ sub process_args {
 				$arg = shift @ARGV or die __("missing --");
 				if ($arg ne '--') {
 					$patch_mode_revision = $arg;
+
+					# NEEDSWORK: Instead of comparing to the literal "HEAD",
+					# compare the commit objects instead so that other ways of
+					# saying the same thing (such as "@") are also handled
+					# appropriately.
+					#
+					# This applies to the cases below too.
 					$patch_mode = ($arg eq 'HEAD' ?
 						       'reset_head' : 'reset_nothead');
 					$arg = shift @ARGV or die __("missing --");

t/t2016-checkout-patch.sh

@@ -18,6 +18,10 @@ test_expect_success PERL 'setup' '
 
 # note: bar sorts before dir/foo, so the first 'n' is always to skip 'bar'
 
+# NEEDSWORK: Since the builtin add-p is used when $GIT_TEST_ADD_I_USE_BUILTIN
+# is given, we should replace the PERL prerequisite with an ADD_I prerequisite
+# which first checks if $GIT_TEST_ADD_I_USE_BUILTIN is defined before checking
+# PERL.
 test_expect_success PERL 'saying "n" does nothing' '
 	set_and_save_state dir/foo work head &&
 	test_write_lines n n | git checkout -p &&
@@ -59,6 +63,13 @@ test_expect_success PERL 'git checkout -p HEAD with change already staged' '
 	verify_state dir/foo head head
 '
 
+test_expect_success PERL 'git checkout -p HEAD^...' '
+	# the third n is to get out in case it mistakenly does not apply
+	test_write_lines n y n | git checkout -p HEAD^... &&
+	verify_saved_state bar &&
+	verify_state dir/foo parent parent
+'
+
 test_expect_success PERL 'git checkout -p HEAD^' '
 	# the third n is to get out in case it mistakenly does not apply
 	test_write_lines n y n | git checkout -p HEAD^ &&

t/t2071-restore-patch.sh

@@ -60,6 +60,14 @@ test_expect_success PERL 'git restore -p --source=HEAD^' '
 	verify_state dir/foo parent index
 '
 
+test_expect_success PERL 'git restore -p --source=HEAD^...' '
+	set_state dir/foo work index &&
+	# the third n is to get out in case it mistakenly does not apply
+	test_write_lines n y n | git restore -p --source=HEAD^... &&
+	verify_saved_state bar &&
+	verify_state dir/foo parent index
+'
+
 test_expect_success PERL 'git restore -p handles deletion' '
 	set_state dir/foo work index &&
 	rm dir/foo &&