patchgit-add: allow path limiting with -u

builtin-add.c, t/t2200-add-update.sh

diff --git a/builtin-add.c b/builtin-add.c
index 5e6748f..1591171 100644
--- a/builtin-add.c
+++ b/builtin-add.c
@@ -16,7 +16,7 @@
 static const char builtin_add_usage[] =
 "git-add [-n] [-v] [-f] [--interactive | -i] [-u] [--] <filepattern>...";
 
-static int take_all_worktree_changes;
+static int take_worktree_changes;
 static const char *excludes_file;
 
 static void prune_directory(struct dir_struct *dir, const char **pathspec, int prefix)
@@ -122,11 +122,12 @@ static void update_callback(struct diff_queue_struct *q,
 	}
 }
 
-static void update_all(int verbose)
+static void update(int verbose, const char **files)
 {
 	struct rev_info rev;
 	init_revisions(&rev, "");
 	setup_revisions(0, NULL, &rev, NULL);
+	rev.prune_data = get_pathspec(rev.prefix, files);
 	rev.diffopt.output_format = DIFF_FORMAT_CALLBACK;
 	rev.diffopt.format_callback = update_callback;
 	rev.diffopt.format_callback_data = &verbose;
@@ -200,16 +201,14 @@ int cmd_add(int argc, const char **argv, const char *prefix)
 			continue;
 		}
 		if (!strcmp(arg, "-u")) {
-			take_all_worktree_changes = 1;
+			take_worktree_changes = 1;
 			continue;
 		}
 		usage(builtin_add_usage);
 	}
 
-	if (take_all_worktree_changes) {
-		if (i < argc)
-			die("-u and explicit paths are incompatible");
-		update_all(verbose);
+	if (take_worktree_changes) {
+		update(verbose, argv + i);
 		goto finish;
 	}
 
diff --git a/t/t2200-add-update.sh b/t/t2200-add-update.sh
new file mode 100755
index 0000000..83005e7
--- /dev/null
+++ b/t/t2200-add-update.sh
@@ -0,0 +1,38 @@
+#!/bin/sh
+
+test_description='git-add -u with path limiting
+
+This test creates a working tree state with three files:
+
+  top (previously committed, modified)
+  dir/sub (previously committed, modified)
+  dir/other (untracked)
+
+and issues a git-add -u with path limiting on "dir" to add
+only the updates to dir/sub.'
+
+. ./test-lib.sh
+
+test_expect_success 'setup' '
+echo initial >top &&
+mkdir dir &&
+echo initial >dir/sub &&
+git-add dir/sub top &&
+git-commit -m initial &&
+echo changed >top &&
+echo changed >dir/sub &&
+echo other >dir/other
+'
+
+test_expect_success 'update' 'git-add -u dir'
+
+test_expect_success 'update touched correct path' \
+  'test "`git-diff-files --name-status dir/sub`" = ""'
+
+test_expect_success 'update did not touch other tracked files' \
+  'test "`git-diff-files --name-status top`" = "M	top"'
+
+test_expect_success 'update did not touch untracked files' \
+  'test "`git-diff-files --name-status dir/other`" = ""'
+
+test_done

diff --git a/Documentation/git-add.txt b/Documentation/git-add.txt
index ea27018..27b9c0f 100644
--- a/Documentation/git-add.txt
+++ b/Documentation/git-add.txt
@@ -57,8 +57,11 @@ OPTIONS
 	the index.
 
 -u::
-	Update all files that git already knows about. This is what
-	"git commit -a" does in preparation for making a commit.
+	Update only files that git already knows about. This is similar
+	to what "git commit -a" does in preparation for making a commit,
+	except that the update is limited to paths specified on the
+	command line. If no paths are specified, all tracked files are
+	updated.
 
 \--::
 	This option can be used to separate command-line options from

@@ -7,7 +7,9 @@ git-add - Add file contents to the changeset to be committed next
 
 SYNOPSIS
 --------
-'git-add' [-n] [-v] [-f] [--interactive | -i] [-u] [--] <file>...
+'git-add' [-n] [-v] [-f] [--] <file>...
+'git-add' [-n] [-v] [-f] -u [[--] <file>...]
+'git-add' (--interactive | -i)
 
 DESCRIPTION
 -----------

This ensures that while git-add without -u needs explicit paths
(even if it is '.'), git-add with -u can have explicit paths but
doesn't need them.