[PATCH 11/16] mktree: create tree using an in-core index

["Victoria Dye via GitGitGadget" <gitgitgadget@gmail.com>]

From: Victoria Dye <vdye@github.com>

Rather than manually write out the contents of a tree object file, construct
an in-memory sparse index from the provided tree entries and create the tree
by writing out its corresponding cache tree.

This patch does not change the behavior of the 'mktree' command. However,
constructing the tree this way will substantially simplify future extensions
to the command's functionality, including handling deeper-than-toplevel tree
entries and applying the provided entries to an existing tree.

Signed-off-by: Victoria Dye <vdye@github.com>
---
 builtin/mktree.c | 74 +++++++++++++++++++++++++++++++++++-------------
 1 file changed, 55 insertions(+), 19 deletions(-)

diff --git a/builtin/mktree.c b/builtin/mktree.c
index e9e2134136f..12f68187221 100644
--- a/builtin/mktree.c
+++ b/builtin/mktree.c
@@ -4,6 +4,7 @@
  * Copyright (c) Junio C Hamano, 2006, 2009
  */
 #include "builtin.h"
+#include "cache-tree.h"
 #include "gettext.h"
 #include "hex.h"
 #include "index-info.h"
@@ -24,6 +25,11 @@ struct tree_entry {
 	char name[FLEX_ARRAY];
 };
 
+static inline size_t df_path_len(size_t pathlen, unsigned int mode)
+{
+	return S_ISDIR(mode) ? pathlen - 1 : pathlen;
+}
+
 struct tree_entry_array {
 	size_t nr, alloc;
 	struct tree_entry **entries;
@@ -57,17 +63,25 @@ static void append_to_tree(unsigned mode, struct object_id *oid, const char *pat
 	if (literally) {
 		FLEX_ALLOC_MEM(ent, name, path, len);
 	} else {
+		size_t len_to_copy = len;
+
 		/* Normalize and validate entry path */
 		if (S_ISDIR(mode)) {
-			while(len > 0 && is_dir_sep(path[len - 1]))
-				len--;
+			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 */
 		}
-		FLEX_ALLOC_MEM(ent, name, path, len);
+		ent = xcalloc(1, st_add3(sizeof(struct tree_entry), len, 1));
+		memcpy(ent->name, path, len_to_copy);
 
 		if (!verify_path(ent->name, mode))
 			die(_("invalid path '%s'"), path);
 		if (strchr(ent->name, '/'))
 			die("path %s contains slash", path);
+
+		/* Add trailing slash to dir */
+		if (S_ISDIR(mode))
+			ent->name[len - 1] = '/';
 	}
 
 	ent->mode = mode;
@@ -86,11 +100,14 @@ static int ent_compare(const void *a_, const void *b_, void *ctx)
 	struct tree_entry *b = *(struct tree_entry **)b_;
 	int ignore_mode = *((int *)ctx);
 
-	if (ignore_mode)
-		cmp = name_compare(a->name, a->len, b->name, b->len);
-	else
-		cmp = base_name_compare(a->name, a->len, a->mode,
-					b->name, b->len, b->mode);
+	size_t a_len = a->len, b_len = b->len;
+
+	if (ignore_mode) {
+		a_len = df_path_len(a_len, a->mode);
+		b_len = df_path_len(b_len, b->mode);
+	}
+
+	cmp = name_compare(a->name, a_len, b->name, b_len);
 	return cmp ? cmp : b->order - a->order;
 }
 
@@ -106,8 +123,8 @@ static void sort_and_dedup_tree_entry_array(struct tree_entry_array *arr)
 	for (size_t i = 0; i < count; i++) {
 		struct tree_entry *curr = arr->entries[i];
 		if (prev &&
-		    !name_compare(prev->name, prev->len,
-				  curr->name, curr->len)) {
+		    !name_compare(prev->name, df_path_len(prev->len, prev->mode),
+				  curr->name, df_path_len(curr->len, curr->mode))) {
 			FREE_AND_NULL(curr);
 		} else {
 			arr->entries[arr->nr++] = curr;
@@ -120,24 +137,43 @@ static void sort_and_dedup_tree_entry_array(struct tree_entry_array *arr)
 	QSORT_S(arr->entries, arr->nr, ent_compare, &ignore_mode);
 }
 
+static int add_tree_entry_to_index(struct index_state *istate,
+				   struct tree_entry *ent)
+{
+	struct cache_entry *ce;
+	struct strbuf ce_name = STRBUF_INIT;
+	strbuf_add(&ce_name, ent->name, ent->len);
+
+	ce = make_cache_entry(istate, ent->mode, &ent->oid, ent->name, 0, 0);
+	if (!ce)
+		return error(_("make_cache_entry failed for path '%s'"), ent->name);
+
+	add_index_entry(istate, ce, ADD_CACHE_JUST_APPEND);
+	strbuf_release(&ce_name);
+	return 0;
+}
+
 static void write_tree(struct tree_entry_array *arr, struct object_id *oid)
 {
-	struct strbuf buf;
-	size_t size = 0;
+	struct index_state istate = INDEX_STATE_INIT(the_repository);
+	istate.sparse_index = 1;
 
 	sort_and_dedup_tree_entry_array(arr);
-	for (size_t i = 0; i < arr->nr; i++)
-		size += 32 + arr->entries[i]->len;
 
-	strbuf_init(&buf, size);
+	/* Construct an in-memory index from the provided entries */
 	for (size_t i = 0; i < arr->nr; i++) {
 		struct tree_entry *ent = arr->entries[i];
-		strbuf_addf(&buf, "%o %s%c", ent->mode, ent->name, '\0');
-		strbuf_add(&buf, ent->oid.hash, the_hash_algo->rawsz);
+
+		if (add_tree_entry_to_index(&istate, ent))
+			die(_("failed to add tree entry '%s'"), ent->name);
 	}
 
-	write_object_file(buf.buf, buf.len, OBJ_TREE, oid);
-	strbuf_release(&buf);
+	/* Write out new tree */
+	if (cache_tree_update(&istate, WRITE_TREE_SILENT | WRITE_TREE_MISSING_OK))
+		die(_("failed to write tree"));
+	oidcpy(oid, &istate.cache_tree->oid);
+
+	release_index(&istate);
 }
 
 static void write_tree_literally(struct tree_entry_array *arr,
-- 
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