built-in add -i: implement the patch command

Well, it is not a full implementation yet. In the interest of making
this easy to review (and easy to keep bugs out), we still hand off to
the Perl script to do the actual work.

The `patch` functionality actually makes up for more than half of the
1,800+ lines of `git-add--interactive.perl`. It will be ported from Perl
to C incrementally, later.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>

add-interactive.c

@@ -9,6 +9,8 @@
 #include "lockfile.h"
 #include "pathspec.h"
 #include "dir.h"
+#include "argv-array.h"
+#include "run-command.h"
 
 struct add_i_state {
 	struct repository *r;
@@ -255,7 +257,7 @@ static ssize_t list_and_choose(struct prefix_item **items, int *selected,
 
 struct adddel {
 	uintmax_t add, del;
-	unsigned seen:1, binary:1;
+	unsigned seen:1, unmerged:1, binary:1;
 };
 
 struct file_list {
@@ -322,6 +324,7 @@ struct collection_status {
 	const char *reference;
 
 	unsigned skip_unseen:1;
+	size_t unmerged_count, binary_count;
 	struct file_list *list;
 	struct hashmap file_map;
 };
@@ -345,12 +348,14 @@ static void collect_changes_cb(struct diff_queue_struct *q,
 		struct pathname_entry *entry;
 		size_t file_index;
 		struct file_item *file;
-		struct adddel *adddel;
+		struct adddel *adddel, *other_adddel;
 
 		entry = hashmap_get_from_hash(&s->file_map, hash, name);
-		if (entry)
+		if (entry) {
+			if (entry->index == (size_t)-1)
+				continue;
 			file_index = entry->index;
-		else if (s->skip_unseen)
+		} else if (s->skip_unseen)
 			continue;
 		else {
 			FLEX_ALLOC_STR(entry, pathname, name);
@@ -363,11 +368,20 @@ static void collect_changes_cb(struct diff_queue_struct *q,
 		file = s->list->file[file_index];
 
 		adddel = s->phase == FROM_INDEX ? &file->index : &file->worktree;
+		other_adddel = s->phase == FROM_INDEX ? &file->worktree : &file->index;
 		adddel->seen = 1;
 		adddel->add = stat.files[i]->added;
 		adddel->del = stat.files[i]->deleted;
-		if (stat.files[i]->is_binary)
+		if (stat.files[i]->is_binary) {
+			if (!other_adddel->binary)
+				s->binary_count++;
 			adddel->binary = 1;
+		}
+		if (stat.files[i]->is_unmerged) {
+			if (!other_adddel->unmerged)
+				s->unmerged_count++;
+			adddel->unmerged = 1;
+		}
 	}
 }
 
@@ -379,6 +393,8 @@ enum modified_files_filter {
 
 static int get_modified_files(struct repository *r,
 			      enum modified_files_filter filter,
+			      size_t *unmerged_count,
+			      size_t *binary_count,
 			      struct file_list *list,
 			      const struct pathspec *ps)
 {
@@ -425,6 +441,10 @@ static int get_modified_files(struct repository *r,
 		}
 	}
 	hashmap_free(&s.file_map, 1);
+	if (unmerged_count)
+		*unmerged_count = s.unmerged_count;
+	if (binary_count)
+		*binary_count = s.binary_count;
 
 	/* While the diffs are ordered already, we ran *two* diffs... */
 	QSORT(list->file, list->nr, file_item_cmp);
@@ -509,7 +529,7 @@ static int run_status(struct add_i_state *s, const struct pathspec *ps,
 {
 	reset_file_list(files);
 
-	if (get_modified_files(s->r, 0, files, ps) < 0)
+	if (get_modified_files(s->r, 0, NULL, NULL, files, ps) < 0)
 		return -1;
 
 	if (files->nr)
@@ -530,7 +550,7 @@ static int run_update(struct add_i_state *s, const struct pathspec *ps,
 
 	reset_file_list(files);
 
-	if (get_modified_files(s->r, WORKTREE_ONLY, files, ps) < 0)
+	if (get_modified_files(s->r, WORKTREE_ONLY, NULL, NULL, files, ps) < 0)
 		return -1;
 
 	if (!files->nr) {
@@ -616,7 +636,7 @@ static int run_revert(struct add_i_state *s, const struct pathspec *ps,
 	struct diff_options diffopt = { NULL };
 
 	reset_file_list(files);
-	if (get_modified_files(s->r, INDEX_ONLY, files, ps) < 0)
+	if (get_modified_files(s->r, INDEX_ONLY, NULL, NULL, files, ps) < 0)
 		return -1;
 
 	if (!files->nr) {
@@ -774,6 +794,64 @@ finish_add_untracked:
 	return res;
 }
 
+static int run_patch(struct add_i_state *s, const struct pathspec *ps,
+		     struct file_list *files,
+		     struct list_and_choose_options *opts)
+{
+	struct prefix_item **items = (struct prefix_item **)files->file;
+	int res = 0, *selected = NULL;
+	ssize_t count, i, j;
+	size_t unmerged_count = 0, binary_count = 0;
+
+	reset_file_list(files);
+	if (get_modified_files(s->r, WORKTREE_ONLY, &unmerged_count,
+			       &binary_count, files, ps) < 0)
+		return -1;
+
+	if (unmerged_count || binary_count) {
+		for (i = j = 0; i < files->nr; i++)
+			if (files->file[i]->index.binary ||
+			    files->file[i]->worktree.binary)
+				free(items[i]);
+			else if (files->file[i]->index.unmerged ||
+				 files->file[i]->worktree.unmerged) {
+				color_fprintf_ln(stderr, s->error_color,
+						 _("ignoring unmerged: %s"),
+						 files->file[i]->item.name);
+				free(items[i]);
+			} else
+				items[j++] = items[i];
+		files->nr = j;
+	}
+
+	if (!files->nr) {
+		if (binary_count)
+			fprintf(stderr, _("Only binary files changed.\n"));
+		else
+			fprintf(stderr, _("No changes.\n"));
+		return 0;
+	}
+
+	opts->prompt = N_("Patch update");
+	CALLOC_ARRAY(selected, files->nr);
+
+	count = list_and_choose(items, selected, files->nr, s, opts);
+	if (count >= 0) {
+		struct argv_array args = ARGV_ARRAY_INIT;
+
+		argv_array_pushl(&args, "git", "add--interactive", "--patch",
+				 "--", NULL);
+		for (i = 0; i < files->nr; i++)
+			if (selected[i])
+				argv_array_push(&args, items[i]->name);
+		res = run_command_v_opt(args.argv, 0);
+		argv_array_clear(&args);
+	}
+
+	free(selected);
+	return res;
+}
+
 static int run_help(struct add_i_state *s, const struct pathspec *ps,
 		    struct file_list *files,
 		    struct list_and_choose_options *opts)
@@ -867,10 +945,11 @@ int run_add_i(struct repository *r, const struct pathspec *ps)
 		update = { { "update" }, run_update },
 		revert = { { "revert" }, run_revert },
 		add_untracked = { { "add untracked" }, run_add_untracked },
+		patch = { { "patch" }, run_patch },
 		help = { { "help" }, run_help };
 	struct command_item *commands[] = {
 		&status, &update, &revert, &add_untracked,
-		&help
+		&patch, &help
 	};
 
 	struct print_file_item_data print_file_item_data = {