[RFC PATCH v3 2/5] dir-iterator: add flags parameter to dir_iterator_begin

["Ævar Arnfjörð Bjarmason" <avarab@gmail.com>]

From: Matheus Tavares <matheus.bernardino@usp.br>

Add the possibility of giving flags to dir_iterator_begin to initialize
a dir-iterator with special options.

Currently possible flags are DIR_ITERATOR_PEDANTIC, which makes
dir_iterator_advance abort imediatelly in the case of an error while
trying to fetch next entry; and DIR_ITERATOR_FOLLOW_SYMLINKS, which
makes the iteration follow symlinks to directories and include its
contents in the iteration. These new flags will be used in a subsequent
patch.

Also adjust refs/files-backend.c to the new dir_iterator_begin
signature.

Signed-off-by: Matheus Tavares <matheus.bernardino@usp.br>
---
 dir-iterator.c       | 28 +++++++++++++++++++++++++---
 dir-iterator.h       | 40 ++++++++++++++++++++++++++++++++--------
 refs/files-backend.c |  2 +-
 3 files changed, 58 insertions(+), 12 deletions(-)

diff --git a/dir-iterator.c b/dir-iterator.c
index f2dcd82fde..17aca8ea41 100644
--- a/dir-iterator.c
+++ b/dir-iterator.c
@@ -48,12 +48,16 @@ struct dir_iterator_int {
 	 * that will be included in this iteration.
 	 */
 	struct dir_iterator_level *levels;
+
+	/* Combination of flags for this dir-iterator */
+	unsigned flags;
 };
 
 int dir_iterator_advance(struct dir_iterator *dir_iterator)
 {
 	struct dir_iterator_int *iter =
 		(struct dir_iterator_int *)dir_iterator;
+	int ret;
 
 	while (1) {
 		struct dir_iterator_level *level =
@@ -71,6 +75,8 @@ int dir_iterator_advance(struct dir_iterator *dir_iterator)
 
 			level->dir = opendir(iter->base.path.buf);
 			if (!level->dir && errno != ENOENT) {
+				if (iter->flags & DIR_ITERATOR_PEDANTIC)
+					goto error_out;
 				warning("error opening directory %s: %s",
 					iter->base.path.buf, strerror(errno));
 				/* Popping the level is handled below */
@@ -122,6 +128,8 @@ int dir_iterator_advance(struct dir_iterator *dir_iterator)
 			if (!de) {
 				/* This level is exhausted; pop up a level. */
 				if (errno) {
+					if (iter->flags & DIR_ITERATOR_PEDANTIC)
+						goto error_out;
 					warning("error reading directory %s: %s",
 						iter->base.path.buf, strerror(errno));
 				} else if (closedir(level->dir))
@@ -138,11 +146,20 @@ int dir_iterator_advance(struct dir_iterator *dir_iterator)
 				continue;
 
 			strbuf_addstr(&iter->base.path, de->d_name);
-			if (lstat(iter->base.path.buf, &iter->base.st) < 0) {
-				if (errno != ENOENT)
+
+			if (iter->flags & DIR_ITERATOR_FOLLOW_SYMLINKS)
+				ret = stat(iter->base.path.buf, &iter->base.st);
+			else
+				ret = lstat(iter->base.path.buf, &iter->base.st);
+
+			if (ret < 0) {
+				if (errno != ENOENT) {
+					if (iter->flags & DIR_ITERATOR_PEDANTIC)
+						goto error_out;
 					warning("error reading path '%s': %s",
 						iter->base.path.buf,
 						strerror(errno));
+				}
 				continue;
 			}
 
@@ -159,6 +176,10 @@ int dir_iterator_advance(struct dir_iterator *dir_iterator)
 			return ITER_OK;
 		}
 	}
+
+error_out:
+	dir_iterator_abort(dir_iterator);
+	return ITER_ERROR;
 }
 
 int dir_iterator_abort(struct dir_iterator *dir_iterator)
@@ -182,7 +203,7 @@ int dir_iterator_abort(struct dir_iterator *dir_iterator)
 	return ITER_DONE;
 }
 
-struct dir_iterator *dir_iterator_begin(const char *path)
+struct dir_iterator *dir_iterator_begin(const char *path, unsigned flags)
 {
 	struct dir_iterator_int *iter = xcalloc(1, sizeof(*iter));
 	struct dir_iterator *dir_iterator = &iter->base;
@@ -195,6 +216,7 @@ struct dir_iterator *dir_iterator_begin(const char *path)
 
 	ALLOC_GROW(iter->levels, 10, iter->levels_alloc);
 
+	iter->flags = flags;
 	iter->levels_nr = 1;
 	iter->levels[0].initialized = 0;
 
diff --git a/dir-iterator.h b/dir-iterator.h
index 970793d07a..fe9eb9a04b 100644
--- a/dir-iterator.h
+++ b/dir-iterator.h
@@ -6,9 +6,10 @@
 /*
  * Iterate over a directory tree.
  *
- * Iterate over a directory tree, recursively, including paths of all
- * types and hidden paths. Skip "." and ".." entries and don't follow
- * symlinks except for the original path.
+ * With no flags to modify behaviour, iterate over a directory tree,
+ * recursively, including paths of all types and hidden paths. Skip
+ * "." and ".." entries and don't follow symlinks except for the
+ * original path.
  *
  * Every time dir_iterator_advance() is called, update the members of
  * the dir_iterator structure to reflect the next path in the
@@ -19,7 +20,7 @@
  * A typical iteration looks like this:
  *
  *     int ok;
- *     struct iterator *iter = dir_iterator_begin(path);
+ *     struct iterator *iter = dir_iterator_begin(path, 0);
  *
  *     while ((ok = dir_iterator_advance(iter)) == ITER_OK) {
  *             if (want_to_stop_iteration()) {
@@ -40,6 +41,20 @@
  * dir_iterator_advance() again.
  */
 
+/*
+ * Flags for dir_iterator_begin:
+ *
+ * - DIR_ITERATOR_PEDANTIC: override dir-iterator's default behavior
+ *   in case of an error while trying to fetch the next entry, which is
+ *   to emit a warning and keep going. With this flag, resouces are
+ *   freed and ITER_ERROR is return immediately.
+ *
+ * - DIR_ITERATOR_FOLLOW_SYMLINKS: make dir-iterator follow symlinks to
+ *   directories, i.e., iterate over linked directories' contents.
+ */
+#define DIR_ITERATOR_PEDANTIC (1 << 0)
+#define DIR_ITERATOR_FOLLOW_SYMLINKS (1 << 1)
+
 struct dir_iterator {
 	/* The current path: */
 	struct strbuf path;
@@ -59,15 +74,19 @@ struct dir_iterator {
 };
 
 /*
- * Start a directory iteration over path. Return a dir_iterator that
- * holds the internal state of the iteration.
+ * Start a directory iteration over path with the combination of
+ * options specified by flags. Return a dir_iterator that holds the
+ * internal state of the iteration.
  *
  * The iteration includes all paths under path, not including path
  * itself and not including "." or ".." entries.
  *
- * path is the starting directory. An internal copy will be made.
+ * Parameters are:
+ *  - path is the starting directory. An internal copy will be made.
+ *  - flags is a combination of the possible flags to initialize a
+ *    dir-iterator or 0 for default behaviour.
  */
-struct dir_iterator *dir_iterator_begin(const char *path);
+struct dir_iterator *dir_iterator_begin(const char *path, unsigned flags);
 
 /*
  * Advance the iterator to the first or next item and return ITER_OK.
@@ -76,6 +95,11 @@ struct dir_iterator *dir_iterator_begin(const char *path);
  * dir_iterator and associated resources and return ITER_ERROR. It is
  * a bug to use iterator or call this function again after it has
  * returned ITER_DONE or ITER_ERROR.
+ *
+ * Note that whether dir-iterator will return ITER_ERROR when failing
+ * to fetch the next entry or just emit a warning and try to fetch the
+ * next is defined by the 'pedantic' option at dir-iterator's
+ * initialization.
  */
 int dir_iterator_advance(struct dir_iterator *iterator);
 
diff --git a/refs/files-backend.c b/refs/files-backend.c
index dd8abe9185..c3d3b6c454 100644
--- a/refs/files-backend.c
+++ b/refs/files-backend.c
@@ -2143,7 +2143,7 @@ static struct ref_iterator *reflog_iterator_begin(struct ref_store *ref_store,
 
 	base_ref_iterator_init(ref_iterator, &files_reflog_iterator_vtable, 0);
 	strbuf_addf(&sb, "%s/logs", gitdir);
-	iter->dir_iterator = dir_iterator_begin(sb.buf);
+	iter->dir_iterator = dir_iterator_begin(sb.buf, 0);
 	iter->ref_store = ref_store;
 	strbuf_release(&sb);
 
-- 
2.21.0.rc2.261.ga7da99ff1b