merge(third_party/git): Merge squashed git subtree at v2.23.0

Merge commit '1b593e1ea4' as 'third_party/git'

third_party/git/decorate.c

@@ -0,0 +1,83 @@
+/*
+ * decorate.c - decorate a git object with some arbitrary
+ * data.
+ */
+#include "cache.h"
+#include "object.h"
+#include "decorate.h"
+
+static unsigned int hash_obj(const struct object *obj, unsigned int n)
+{
+	return oidhash(&obj->oid) % n;
+}
+
+static void *insert_decoration(struct decoration *n, const struct object *base, void *decoration)
+{
+	int size = n->size;
+	struct decoration_entry *entries = n->entries;
+	unsigned int j = hash_obj(base, size);
+
+	while (entries[j].base) {
+		if (entries[j].base == base) {
+			void *old = entries[j].decoration;
+			entries[j].decoration = decoration;
+			return old;
+		}
+		if (++j >= size)
+			j = 0;
+	}
+	entries[j].base = base;
+	entries[j].decoration = decoration;
+	n->nr++;
+	return NULL;
+}
+
+static void grow_decoration(struct decoration *n)
+{
+	int i;
+	int old_size = n->size;
+	struct decoration_entry *old_entries = n->entries;
+
+	n->size = (old_size + 1000) * 3 / 2;
+	n->entries = xcalloc(n->size, sizeof(struct decoration_entry));
+	n->nr = 0;
+
+	for (i = 0; i < old_size; i++) {
+		const struct object *base = old_entries[i].base;
+		void *decoration = old_entries[i].decoration;
+
+		if (!decoration)
+			continue;
+		insert_decoration(n, base, decoration);
+	}
+	free(old_entries);
+}
+
+void *add_decoration(struct decoration *n, const struct object *obj,
+		void *decoration)
+{
+	int nr = n->nr + 1;
+
+	if (nr > n->size * 2 / 3)
+		grow_decoration(n);
+	return insert_decoration(n, obj, decoration);
+}
+
+void *lookup_decoration(struct decoration *n, const struct object *obj)
+{
+	unsigned int j;
+
+	/* nothing to lookup */
+	if (!n->size)
+		return NULL;
+	j = hash_obj(obj, n->size);
+	for (;;) {
+		struct decoration_entry *ref = n->entries + j;
+		if (ref->base == obj)
+			return ref->decoration;
+		if (!ref->base)
+			return NULL;
+		if (++j == n->size)
+			j = 0;
+	}
+}