mktree: remove entries when mode is 0

If tree entries are specified with a mode with value '0', remove them from
the tree instead of adding/updating them. If the mode is '0', both the
provided type string (if specified) and the object ID of the entry are
ignored.

Note that entries with mode '0' are added to the 'struct tree_ent_array'
with a trailing slash so that it's always treated like a directory. This is
a bit of a hack to ensure that the removal supercedes any preceding entries
with matching names, as well as any nested inside a directory matching its
name.

Signed-off-by: Victoria Dye <[email protected]>

Documentation/git-mktree.txt

@@ -63,6 +63,10 @@ entries nested within one or more directories. These entries are inserted
 into the appropriate tree in the base tree-ish if one exists. Otherwise,
 empty parent trees are created to contain the entries.
 
+An entry with a mode of "0" will remove an entry of the same name from the
+base tree-ish. If no tree-ish argument is given, or the entry does not exist
+in that tree, the entry is ignored.
+
 The order of the tree entries is normalized by `mktree` so pre-sorting the
 input by path is not required. Multiple entries provided with the same path
 are deduplicated, with only the last one specified added to the tree.

builtin/mktree.c

@@ -32,7 +32,7 @@ struct tree_entry {
 
 static inline size_t df_path_len(size_t pathlen, unsigned int mode)
 {
-	return S_ISDIR(mode) ? pathlen - 1 : pathlen;
+	return (S_ISDIR(mode) || !mode) ? pathlen - 1 : pathlen;
 }
 
 struct tree_entry_array {
@@ -108,7 +108,7 @@ static void append_to_tree(unsigned mode, struct object_id *oid, const char *pat
 		size_t len_to_copy = len;
 
 		/* Normalize and validate entry path */
-		if (S_ISDIR(mode)) {
+		if (S_ISDIR(mode) || !mode) {
 			while(len_to_copy > 0 && is_dir_sep(path[len_to_copy - 1]))
 				len_to_copy--;
 			len = len_to_copy + 1; /* add space for trailing slash */
@@ -124,7 +124,7 @@ static void append_to_tree(unsigned mode, struct object_id *oid, const char *pat
 			arr->has_nested_entries = 1;
 
 		/* Add trailing slash to dir */
-		if (S_ISDIR(mode))
+		if (S_ISDIR(mode) || !mode)
 			ent->name[len - 1] = '/';
 	}
 
@@ -209,7 +209,7 @@ static void sort_and_dedup_tree_entry_array(struct tree_entry_array *arr)
 
 			if (!skip_entry) {
 				arr->entries[arr->nr++] = curr;
-				if (S_ISDIR(curr->mode))
+				if (S_ISDIR(curr->mode) || !curr->mode)
 					tree_entry_array_push(&parent_dir_ents, curr);
 			} else {
 				FREE_AND_NULL(curr);
@@ -270,6 +270,9 @@ static int build_index_from_tree(const struct object_id *oid,
 static int add_tree_entry_to_index(struct build_index_data *data,
 				   struct tree_entry *ent)
 {
+	if (!ent->mode)
+		return 0;
+
 	if (ent->expand_dir) {
 		int ret = 0;
 		struct pathspec ps = { 0 };
@@ -450,6 +453,10 @@ static int mktree_line(unsigned int mode, struct object_id *oid,
 	if (stage)
 		die(_("path '%s' is unmerged"), path);
 
+	/* OID ignored for zero-mode entries; append unconditionally */
+	if (!mode)
+		goto append_entry;
+
 	if (obj_type != OBJ_ANY && mode_type != obj_type)
 		die("object type (%s) doesn't match mode type (%s)",
 		    type_name(obj_type), type_name(mode_type));
@@ -484,6 +491,7 @@ static int mktree_line(unsigned int mode, struct object_id *oid,
 		}
 	}
 
+append_entry:
 	append_to_tree(mode, oid, path, data->arr, data->literally);
 	return 0;
 }

t/t1010-mktree.sh

@@ -369,4 +369,42 @@ test_expect_success 'mktree fails on directory-file conflict' '
 	test_grep "You have both folder/one and folder/one/deeper/deep" err
 '
 
+test_expect_success 'mktree with remove entries' '
+	tree_oid="$(cat tree)" &&
+	blob_oid="$(git rev-parse $tree_oid:folder.txt)" &&
+
+	{
+		printf "100644 blob $blob_oid\ttest/deeper/deep.txt\n" &&
+		printf "100644 blob $blob_oid\ttest.txt\n" &&
+		printf "100644 blob $blob_oid\texample\n" &&
+		printf "100644 blob $blob_oid\texample.a/file\n" &&
+		printf "100644 blob $blob_oid\texample.txt\n" &&
+		printf "040000 tree $tree_oid\tfolder\n" &&
+		printf "0 $ZERO_OID\tfolder\n" &&
+		printf "0 $ZERO_OID\tmissing\n"
+	} | git mktree >tree.base &&
+
+	{
+		printf "0 $ZERO_OID\texample.txt\n" &&
+		printf "0 $ZERO_OID\ttest/deeper\n"
+	} | git mktree $(cat tree.base) >tree.actual &&
+
+	{
+		printf "100644 blob $blob_oid\texample\n" &&
+		printf "100644 blob $blob_oid\texample.a/file\n" &&
+		printf "100644 blob $blob_oid\ttest.txt\n"
+	} >expect &&
+	git ls-tree -r $(cat tree.actual) >actual &&
+
+	test_cmp expect actual
+'
+
+test_expect_success 'type and oid not checked if entry mode is 0' '
+	# type and oid do not match
+	printf "0 commit $EMPTY_TREE\tfolder.txt\n" |
+	git mktree >tree.actual &&
+
+	test "$(cat tree.actual)" = $EMPTY_TREE
+'
+
 test_done