Initial commit for TizenHEADsubmit/2.0alpha/20130201.014617accepted/2.0alpha/20130201.0121062.0alpha

1 files changed, 1452 insertions, 0 deletions

diff --git a/unpack-trees.c b/unpack-trees.c
new file mode 100644
index 0000000..8cf0da3
--- /dev/null
+++ b/unpack-trees.c
@@ -0,0 +1,1452 @@
+#define NO_THE_INDEX_COMPATIBILITY_MACROS
+#include "cache.h"
+#include "dir.h"
+#include "tree.h"
+#include "tree-walk.h"
+#include "cache-tree.h"
+#include "unpack-trees.h"
+#include "progress.h"
+#include "refs.h"
+#include "attr.h"
+
+/*
+ * Error messages expected by scripts out of plumbing commands such as
+ * read-tree.  Non-scripted Porcelain is not required to use these messages
+ * and in fact are encouraged to reword them to better suit their particular
+ * situation better.  See how "git checkout" replaces not_uptodate_file to
+ * explain why it does not allow switching between branches when you have
+ * local changes, for example.
+ */
+static struct unpack_trees_error_msgs unpack_plumbing_errors = {
+	/* would_overwrite */
+	"Entry '%s' would be overwritten by merge. Cannot merge.",
+
+	/* not_uptodate_file */
+	"Entry '%s' not uptodate. Cannot merge.",
+
+	/* not_uptodate_dir */
+	"Updating '%s' would lose untracked files in it",
+
+	/* would_lose_untracked */
+	"Untracked working tree file '%s' would be %s by merge.",
+
+	/* bind_overlap */
+	"Entry '%s' overlaps with '%s'.  Cannot bind.",
+
+	/* sparse_not_uptodate_file */
+	"Entry '%s' not uptodate. Cannot update sparse checkout.",
+
+	/* would_lose_orphaned */
+	"Working tree file '%s' would be %s by sparse checkout update.",
+};
+
+#define ERRORMSG(o,fld) \
+	( ((o) && (o)->msgs.fld) \
+	? ((o)->msgs.fld) \
+	: (unpack_plumbing_errors.fld) )
+
+static void add_entry(struct unpack_trees_options *o, struct cache_entry *ce,
+	unsigned int set, unsigned int clear)
+{
+	unsigned int size = ce_size(ce);
+	struct cache_entry *new = xmalloc(size);
+
+	clear |= CE_HASHED | CE_UNHASHED;
+
+	memcpy(new, ce, size);
+	new->next = NULL;
+	new->ce_flags = (new->ce_flags & ~clear) | set;
+	add_index_entry(&o->result, new, ADD_CACHE_OK_TO_ADD|ADD_CACHE_OK_TO_REPLACE);
+}
+
+/*
+ * Unlink the last component and schedule the leading directories for
+ * removal, such that empty directories get removed.
+ */
+static void unlink_entry(struct cache_entry *ce)
+{
+	if (has_symlink_or_noent_leading_path(ce->name, ce_namelen(ce)))
+		return;
+	if (remove_or_warn(ce->ce_mode, ce->name))
+		return;
+	schedule_dir_for_removal(ce->name, ce_namelen(ce));
+}
+
+static struct checkout state;
+static int check_updates(struct unpack_trees_options *o)
+{
+	unsigned cnt = 0, total = 0;
+	struct progress *progress = NULL;
+	struct index_state *index = &o->result;
+	int i;
+	int errs = 0;
+
+	if (o->update && o->verbose_update) {
+		for (total = cnt = 0; cnt < index->cache_nr; cnt++) {
+			struct cache_entry *ce = index->cache[cnt];
+			if (ce->ce_flags & (CE_UPDATE | CE_REMOVE | CE_WT_REMOVE))
+				total++;
+		}
+
+		progress = start_progress_delay("Checking out files",
+						total, 50, 1);
+		cnt = 0;
+	}
+
+	if (o->update)
+		git_attr_set_direction(GIT_ATTR_CHECKOUT, &o->result);
+	for (i = 0; i < index->cache_nr; i++) {
+		struct cache_entry *ce = index->cache[i];
+
+		if (ce->ce_flags & CE_WT_REMOVE) {
+			display_progress(progress, ++cnt);
+			if (o->update)
+				unlink_entry(ce);
+			continue;
+		}
+
+		if (ce->ce_flags & CE_REMOVE) {
+			display_progress(progress, ++cnt);
+			if (o->update)
+				unlink_entry(ce);
+		}
+	}
+	remove_marked_cache_entries(&o->result);
+	remove_scheduled_dirs();
+
+	for (i = 0; i < index->cache_nr; i++) {
+		struct cache_entry *ce = index->cache[i];
+
+		if (ce->ce_flags & CE_UPDATE) {
+			display_progress(progress, ++cnt);
+			ce->ce_flags &= ~CE_UPDATE;
+			if (o->update) {
+				errs |= checkout_entry(ce, &state, NULL);
+			}
+		}
+	}
+	stop_progress(&progress);
+	if (o->update)
+		git_attr_set_direction(GIT_ATTR_CHECKIN, NULL);
+	return errs != 0;
+}
+
+static int verify_uptodate_sparse(struct cache_entry *ce, struct unpack_trees_options *o);
+static int verify_absent_sparse(struct cache_entry *ce, const char *action, struct unpack_trees_options *o);
+
+static int will_have_skip_worktree(const struct cache_entry *ce, struct unpack_trees_options *o)
+{
+	const char *basename;
+
+	if (ce_stage(ce))
+		return 0;
+
+	basename = strrchr(ce->name, '/');
+	basename = basename ? basename+1 : ce->name;
+	return excluded_from_list(ce->name, ce_namelen(ce), basename, NULL, o->el) <= 0;
+}
+
+static int apply_sparse_checkout(struct cache_entry *ce, struct unpack_trees_options *o)
+{
+	int was_skip_worktree = ce_skip_worktree(ce);
+
+	if (will_have_skip_worktree(ce, o))
+		ce->ce_flags |= CE_SKIP_WORKTREE;
+	else
+		ce->ce_flags &= ~CE_SKIP_WORKTREE;
+
+	/*
+	 * We only care about files getting into the checkout area
+	 * If merge strategies want to remove some, go ahead, this
+	 * flag will be removed eventually in unpack_trees() if it's
+	 * outside checkout area.
+	 */
+	if (ce->ce_flags & CE_REMOVE)
+		return 0;
+
+	if (!was_skip_worktree && ce_skip_worktree(ce)) {
+		/*
+		 * If CE_UPDATE is set, verify_uptodate() must be called already
+		 * also stat info may have lost after merged_entry() so calling
+		 * verify_uptodate() again may fail
+		 */
+		if (!(ce->ce_flags & CE_UPDATE) && verify_uptodate_sparse(ce, o))
+			return -1;
+		ce->ce_flags |= CE_WT_REMOVE;
+	}
+	if (was_skip_worktree && !ce_skip_worktree(ce)) {
+		if (verify_absent_sparse(ce, "overwritten", o))
+			return -1;
+		ce->ce_flags |= CE_UPDATE;
+	}
+	return 0;
+}
+
+static inline int call_unpack_fn(struct cache_entry **src, struct unpack_trees_options *o)
+{
+	int ret = o->fn(src, o);
+	if (ret > 0)
+		ret = 0;
+	return ret;
+}
+
+static void mark_ce_used(struct cache_entry *ce, struct unpack_trees_options *o)
+{
+	ce->ce_flags |= CE_UNPACKED;
+
+	if (o->cache_bottom < o->src_index->cache_nr &&
+	    o->src_index->cache[o->cache_bottom] == ce) {
+		int bottom = o->cache_bottom;
+		while (bottom < o->src_index->cache_nr &&
+		       o->src_index->cache[bottom]->ce_flags & CE_UNPACKED)
+			bottom++;
+		o->cache_bottom = bottom;
+	}
+}
+
+static void mark_all_ce_unused(struct index_state *index)
+{
+	int i;
+	for (i = 0; i < index->cache_nr; i++)
+		index->cache[i]->ce_flags &= ~CE_UNPACKED;
+}
+
+static int locate_in_src_index(struct cache_entry *ce,
+			       struct unpack_trees_options *o)
+{
+	struct index_state *index = o->src_index;
+	int len = ce_namelen(ce);
+	int pos = index_name_pos(index, ce->name, len);
+	if (pos < 0)
+		pos = -1 - pos;
+	return pos;
+}
+
+/*
+ * We call unpack_index_entry() with an unmerged cache entry
+ * only in diff-index, and it wants a single callback.  Skip
+ * the other unmerged entry with the same name.
+ */
+static void mark_ce_used_same_name(struct cache_entry *ce,
+				   struct unpack_trees_options *o)
+{
+	struct index_state *index = o->src_index;
+	int len = ce_namelen(ce);
+	int pos;
+
+	for (pos = locate_in_src_index(ce, o); pos < index->cache_nr; pos++) {
+		struct cache_entry *next = index->cache[pos];
+		if (len != ce_namelen(next) ||
+		    memcmp(ce->name, next->name, len))
+			break;
+		mark_ce_used(next, o);
+	}
+}
+
+static struct cache_entry *next_cache_entry(struct unpack_trees_options *o)
+{
+	const struct index_state *index = o->src_index;
+	int pos = o->cache_bottom;
+
+	while (pos < index->cache_nr) {
+		struct cache_entry *ce = index->cache[pos];
+		if (!(ce->ce_flags & CE_UNPACKED))
+			return ce;
+		pos++;
+	}
+	return NULL;
+}
+
+static void add_same_unmerged(struct cache_entry *ce,
+			      struct unpack_trees_options *o)
+{
+	struct index_state *index = o->src_index;
+	int len = ce_namelen(ce);
+	int pos = index_name_pos(index, ce->name, len);
+
+	if (0 <= pos)
+		die("programming error in a caller of mark_ce_used_same_name");
+	for (pos = -pos - 1; pos < index->cache_nr; pos++) {
+		struct cache_entry *next = index->cache[pos];
+		if (len != ce_namelen(next) ||
+		    memcmp(ce->name, next->name, len))
+			break;
+		add_entry(o, next, 0, 0);
+		mark_ce_used(next, o);
+	}
+}
+
+static int unpack_index_entry(struct cache_entry *ce,
+			      struct unpack_trees_options *o)
+{
+	struct cache_entry *src[5] = { NULL };
+	int ret;
+
+	src[0] = ce;
+
+	mark_ce_used(ce, o);
+	if (ce_stage(ce)) {
+		if (o->skip_unmerged) {
+			add_entry(o, ce, 0, 0);
+			return 0;
+		}
+	}
+	ret = call_unpack_fn(src, o);
+	if (ce_stage(ce))
+		mark_ce_used_same_name(ce, o);
+	return ret;
+}
+
+static int find_cache_pos(struct traverse_info *, const struct name_entry *);
+
+static void restore_cache_bottom(struct traverse_info *info, int bottom)
+{
+	struct unpack_trees_options *o = info->data;
+
+	if (o->diff_index_cached)
+		return;
+	o->cache_bottom = bottom;
+}
+
+static int switch_cache_bottom(struct traverse_info *info)
+{
+	struct unpack_trees_options *o = info->data;
+	int ret, pos;
+
+	if (o->diff_index_cached)
+		return 0;
+	ret = o->cache_bottom;
+	pos = find_cache_pos(info->prev, &info->name);
+
+	if (pos < -1)
+		o->cache_bottom = -2 - pos;
+	else if (pos < 0)
+		o->cache_bottom = o->src_index->cache_nr;
+	return ret;
+}
+
+static int traverse_trees_recursive(int n, unsigned long dirmask, unsigned long df_conflicts, struct name_entry *names, struct traverse_info *info)
+{
+	int i, ret, bottom;
+	struct tree_desc t[MAX_UNPACK_TREES];
+	struct traverse_info newinfo;
+	struct name_entry *p;
+
+	p = names;
+	while (!p->mode)
+		p++;
+
+	newinfo = *info;
+	newinfo.prev = info;
+	newinfo.name = *p;
+	newinfo.pathlen += tree_entry_len(p->path, p->sha1) + 1;
+	newinfo.conflicts |= df_conflicts;
+
+	for (i = 0; i < n; i++, dirmask >>= 1) {
+		const unsigned char *sha1 = NULL;
+		if (dirmask & 1)
+			sha1 = names[i].sha1;
+		fill_tree_descriptor(t+i, sha1);
+	}
+
+	bottom = switch_cache_bottom(&newinfo);
+	ret = traverse_trees(n, t, &newinfo);
+	restore_cache_bottom(&newinfo, bottom);
+	return ret;
+}
+
+/*
+ * Compare the traverse-path to the cache entry without actually
+ * having to generate the textual representation of the traverse
+ * path.
+ *
+ * NOTE! This *only* compares up to the size of the traverse path
+ * itself - the caller needs to do the final check for the cache
+ * entry having more data at the end!
+ */
+static int do_compare_entry(const struct cache_entry *ce, const struct traverse_info *info, const struct name_entry *n)
+{
+	int len, pathlen, ce_len;
+	const char *ce_name;
+
+	if (info->prev) {
+		int cmp = do_compare_entry(ce, info->prev, &info->name);
+		if (cmp)
+			return cmp;
+	}
+	pathlen = info->pathlen;
+	ce_len = ce_namelen(ce);
+
+	/* If ce_len < pathlen then we must have previously hit "name == directory" entry */
+	if (ce_len < pathlen)
+		return -1;
+
+	ce_len -= pathlen;
+	ce_name = ce->name + pathlen;
+
+	len = tree_entry_len(n->path, n->sha1);
+	return df_name_compare(ce_name, ce_len, S_IFREG, n->path, len, n->mode);
+}
+
+static int compare_entry(const struct cache_entry *ce, const struct traverse_info *info, const struct name_entry *n)
+{
+	int cmp = do_compare_entry(ce, info, n);
+	if (cmp)
+		return cmp;
+
+	/*
+	 * Even if the beginning compared identically, the ce should
+	 * compare as bigger than a directory leading up to it!
+	 */
+	return ce_namelen(ce) > traverse_path_len(info, n);
+}
+
+static int ce_in_traverse_path(const struct cache_entry *ce,
+			       const struct traverse_info *info)
+{
+	if (!info->prev)
+		return 1;
+	if (do_compare_entry(ce, info->prev, &info->name))
+		return 0;
+	/*
+	 * If ce (blob) is the same name as the path (which is a tree
+	 * we will be descending into), it won't be inside it.
+	 */
+	return (info->pathlen < ce_namelen(ce));
+}
+
+static struct cache_entry *create_ce_entry(const struct traverse_info *info, const struct name_entry *n, int stage)
+{
+	int len = traverse_path_len(info, n);
+	struct cache_entry *ce = xcalloc(1, cache_entry_size(len));
+
+	ce->ce_mode = create_ce_mode(n->mode);
+	ce->ce_flags = create_ce_flags(len, stage);
+	hashcpy(ce->sha1, n->sha1);
+	make_traverse_path(ce->name, info, n);
+
+	return ce;
+}
+
+static int unpack_nondirectories(int n, unsigned long mask,
+				 unsigned long dirmask,
+				 struct cache_entry **src,
+				 const struct name_entry *names,
+				 const struct traverse_info *info)
+{
+	int i;
+	struct unpack_trees_options *o = info->data;
+	unsigned long conflicts;
+
+	/* Do we have *only* directories? Nothing to do */
+	if (mask == dirmask && !src[0])
+		return 0;
+
+	conflicts = info->conflicts;
+	if (o->merge)
+		conflicts >>= 1;
+	conflicts |= dirmask;
+
+	/*
+	 * Ok, we've filled in up to any potential index entry in src[0],
+	 * now do the rest.
+	 */
+	for (i = 0; i < n; i++) {
+		int stage;
+		unsigned int bit = 1ul << i;
+		if (conflicts & bit) {
+			src[i + o->merge] = o->df_conflict_entry;
+			continue;
+		}
+		if (!(mask & bit))
+			continue;
+		if (!o->merge)
+			stage = 0;
+		else if (i + 1 < o->head_idx)
+			stage = 1;
+		else if (i + 1 > o->head_idx)
+			stage = 3;
+		else
+			stage = 2;
+		src[i + o->merge] = create_ce_entry(info, names + i, stage);
+	}
+
+	if (o->merge)
+		return call_unpack_fn(src, o);
+
+	for (i = 0; i < n; i++)
+		if (src[i] && src[i] != o->df_conflict_entry)
+			add_entry(o, src[i], 0, 0);
+	return 0;
+}
+
+static int unpack_failed(struct unpack_trees_options *o, const char *message)
+{
+	discard_index(&o->result);
+	if (!o->gently) {
+		if (message)
+			return error("%s", message);
+		return -1;
+	}
+	return -1;
+}
+
+/* NEEDSWORK: give this a better name and share with tree-walk.c */
+static int name_compare(const char *a, int a_len,
+			const char *b, int b_len)
+{
+	int len = (a_len < b_len) ? a_len : b_len;
+	int cmp = memcmp(a, b, len);
+	if (cmp)
+		return cmp;
+	return (a_len - b_len);
+}
+
+/*
+ * The tree traversal is looking at name p.  If we have a matching entry,
+ * return it.  If name p is a directory in the index, do not return
+ * anything, as we will want to match it when the traversal descends into
+ * the directory.
+ */
+static int find_cache_pos(struct traverse_info *info,
+			  const struct name_entry *p)
+{
+	int pos;
+	struct unpack_trees_options *o = info->data;
+	struct index_state *index = o->src_index;
+	int pfxlen = info->pathlen;
+	int p_len = tree_entry_len(p->path, p->sha1);
+
+	for (pos = o->cache_bottom; pos < index->cache_nr; pos++) {
+		struct cache_entry *ce = index->cache[pos];
+		const char *ce_name, *ce_slash;
+		int cmp, ce_len;
+
+		if (ce->ce_flags & CE_UNPACKED) {
+			/*
+			 * cache_bottom entry is already unpacked, so
+			 * we can never match it; don't check it
+			 * again.
+			 */
+			if (pos == o->cache_bottom)
+				++o->cache_bottom;
+			continue;
+		}
+		if (!ce_in_traverse_path(ce, info))
+			continue;
+		ce_name = ce->name + pfxlen;
+		ce_slash = strchr(ce_name, '/');
+		if (ce_slash)
+			ce_len = ce_slash - ce_name;
+		else
+			ce_len = ce_namelen(ce) - pfxlen;
+		cmp = name_compare(p->path, p_len, ce_name, ce_len);
+		/*
+		 * Exact match; if we have a directory we need to
+		 * delay returning it.
+		 */
+		if (!cmp)
+			return ce_slash ? -2 - pos : pos;
+		if (0 < cmp)
+			continue; /* keep looking */
+		/*
+		 * ce_name sorts after p->path; could it be that we
+		 * have files under p->path directory in the index?
+		 * E.g.  ce_name == "t-i", and p->path == "t"; we may
+		 * have "t/a" in the index.
+		 */
+		if (p_len < ce_len && !memcmp(ce_name, p->path, p_len) &&
+		    ce_name[p_len] < '/')
+			continue; /* keep looking */
+		break;
+	}
+	return -1;
+}
+
+static struct cache_entry *find_cache_entry(struct traverse_info *info,
+					    const struct name_entry *p)
+{
+	int pos = find_cache_pos(info, p);
+	struct unpack_trees_options *o = info->data;
+
+	if (0 <= pos)
+		return o->src_index->cache[pos];
+	else
+		return NULL;
+}
+
+static void debug_path(struct traverse_info *info)
+{
+	if (info->prev) {
+		debug_path(info->prev);
+		if (*info->prev->name.path)
+			putchar('/');
+	}
+	printf("%s", info->name.path);
+}
+
+static void debug_name_entry(int i, struct name_entry *n)
+{
+	printf("ent#%d %06o %s\n", i,
+	       n->path ? n->mode : 0,
+	       n->path ? n->path : "(missing)");
+}
+
+static void debug_unpack_callback(int n,
+				  unsigned long mask,
+				  unsigned long dirmask,
+				  struct name_entry *names,
+				  struct traverse_info *info)
+{
+	int i;
+	printf("* unpack mask %lu, dirmask %lu, cnt %d ",
+	       mask, dirmask, n);
+	debug_path(info);
+	putchar('\n');
+	for (i = 0; i < n; i++)
+		debug_name_entry(i, names + i);
+}
+
+static int unpack_callback(int n, unsigned long mask, unsigned long dirmask, struct name_entry *names, struct traverse_info *info)
+{
+	struct cache_entry *src[MAX_UNPACK_TREES + 1] = { NULL, };
+	struct unpack_trees_options *o = info->data;
+	const struct name_entry *p = names;
+
+	/* Find first entry with a real name (we could use "mask" too) */
+	while (!p->mode)
+		p++;
+
+	if (o->debug_unpack)
+		debug_unpack_callback(n, mask, dirmask, names, info);
+
+	/* Are we supposed to look at the index too? */
+	if (o->merge) {
+		while (1) {
+			int cmp;
+			struct cache_entry *ce;
+
+			if (o->diff_index_cached)
+				ce = next_cache_entry(o);
+			else
+				ce = find_cache_entry(info, p);
+
+			if (!ce)
+				break;
+			cmp = compare_entry(ce, info, p);
+			if (cmp < 0) {
+				if (unpack_index_entry(ce, o) < 0)
+					return unpack_failed(o, NULL);
+				continue;
+			}
+			if (!cmp) {
+				if (ce_stage(ce)) {
+					/*
+					 * If we skip unmerged index
+					 * entries, we'll skip this
+					 * entry *and* the tree
+					 * entries associated with it!
+					 */
+					if (o->skip_unmerged) {
+						add_same_unmerged(ce, o);
+						return mask;
+					}
+				}
+				src[0] = ce;
+			}
+			break;
+		}
+	}
+
+	if (unpack_nondirectories(n, mask, dirmask, src, names, info) < 0)
+		return -1;
+
+	if (src[0]) {
+		if (ce_stage(src[0]))
+			mark_ce_used_same_name(src[0], o);
+		else
+			mark_ce_used(src[0], o);
+	}
+
+	/* Now handle any directories.. */
+	if (dirmask) {
+		unsigned long conflicts = mask & ~dirmask;
+		if (o->merge) {
+			conflicts <<= 1;
+			if (src[0])
+				conflicts |= 1;
+		}
+
+		/* special case: "diff-index --cached" looking at a tree */
+		if (o->diff_index_cached &&
+		    n == 1 && dirmask == 1 && S_ISDIR(names->mode)) {
+			int matches;
+			matches = cache_tree_matches_traversal(o->src_index->cache_tree,
+							       names, info);
+			/*
+			 * Everything under the name matches; skip the
+			 * entire hierarchy.  diff_index_cached codepath
+			 * special cases D/F conflicts in such a way that
+			 * it does not do any look-ahead, so this is safe.
+			 */
+			if (matches) {
+				o->cache_bottom += matches;
+				return mask;
+			}
+		}
+
+		if (traverse_trees_recursive(n, dirmask, conflicts,
+					     names, info) < 0)
+			return -1;
+		return mask;
+	}
+
+	return mask;
+}
+
+/*
+ * N-way merge "len" trees.  Returns 0 on success, -1 on failure to manipulate the
+ * resulting index, -2 on failure to reflect the changes to the work tree.
+ */
+int unpack_trees(unsigned len, struct tree_desc *t, struct unpack_trees_options *o)
+{
+	int i, ret;
+	static struct cache_entry *dfc;
+	struct exclude_list el;
+
+	if (len > MAX_UNPACK_TREES)
+		die("unpack_trees takes at most %d trees", MAX_UNPACK_TREES);
+	memset(&state, 0, sizeof(state));
+	state.base_dir = "";
+	state.force = 1;
+	state.quiet = 1;
+	state.refresh_cache = 1;
+
+	memset(&el, 0, sizeof(el));
+	if (!core_apply_sparse_checkout || !o->update)
+		o->skip_sparse_checkout = 1;
+	if (!o->skip_sparse_checkout) {
+		if (add_excludes_from_file_to_list(git_path("info/sparse-checkout"), "", 0, NULL, &el, 0) < 0)
+			o->skip_sparse_checkout = 1;
+		else
+			o->el = &el;
+	}
+
+	memset(&o->result, 0, sizeof(o->result));
+	o->result.initialized = 1;
+	o->result.timestamp.sec = o->src_index->timestamp.sec;
+	o->result.timestamp.nsec = o->src_index->timestamp.nsec;
+	o->merge_size = len;
+	mark_all_ce_unused(o->src_index);
+
+	if (!dfc)
+		dfc = xcalloc(1, cache_entry_size(0));
+	o->df_conflict_entry = dfc;
+
+	if (len) {
+		const char *prefix = o->prefix ? o->prefix : "";
+		struct traverse_info info;
+
+		setup_traverse_info(&info, prefix);
+		info.fn = unpack_callback;
+		info.data = o;
+
+		if (o->prefix) {
+			/*
+			 * Unpack existing index entries that sort before the
+			 * prefix the tree is spliced into.  Note that o->merge
+			 * is always true in this case.
+			 */
+			while (1) {
+				struct cache_entry *ce = next_cache_entry(o);
+				if (!ce)
+					break;
+				if (ce_in_traverse_path(ce, &info))
+					break;
+				if (unpack_index_entry(ce, o) < 0)
+					goto return_failed;
+			}
+		}
+
+		if (traverse_trees(len, t, &info) < 0)
+			goto return_failed;
+	}
+
+	/* Any left-over entries in the index? */
+	if (o->merge) {
+		while (1) {
+			struct cache_entry *ce = next_cache_entry(o);
+			if (!ce)
+				break;
+			if (unpack_index_entry(ce, o) < 0)
+				goto return_failed;
+		}
+	}
+	mark_all_ce_unused(o->src_index);
+
+	if (o->trivial_merges_only && o->nontrivial_merge) {
+		ret = unpack_failed(o, "Merge requires file-level merging");
+		goto done;
+	}
+
+	if (!o->skip_sparse_checkout) {
+		int empty_worktree = 1;
+		for (i = 0;i < o->result.cache_nr;i++) {
+			struct cache_entry *ce = o->result.cache[i];
+
+			if (apply_sparse_checkout(ce, o)) {
+				ret = -1;
+				goto done;
+			}
+			/*
+			 * Merge strategies may set CE_UPDATE|CE_REMOVE outside checkout
+			 * area as a result of ce_skip_worktree() shortcuts in
+			 * verify_absent() and verify_uptodate(). Clear them.
+			 */
+			if (ce_skip_worktree(ce))
+				ce->ce_flags &= ~(CE_UPDATE | CE_REMOVE);
+			else
+				empty_worktree = 0;
+
+		}
+		if (o->result.cache_nr && empty_worktree) {
+			ret = unpack_failed(o, "Sparse checkout leaves no entry on working directory");
+			goto done;
+		}
+	}
+
+	o->src_index = NULL;
+	ret = check_updates(o) ? (-2) : 0;
+	if (o->dst_index)
+		*o->dst_index = o->result;
+
+done:
+	for (i = 0;i < el.nr;i++)
+		free(el.excludes[i]);
+	if (el.excludes)
+		free(el.excludes);
+
+	return ret;
+
+return_failed:
+	mark_all_ce_unused(o->src_index);
+	ret = unpack_failed(o, NULL);
+	goto done;
+}
+
+/* Here come the merge functions */
+
+static int reject_merge(struct cache_entry *ce, struct unpack_trees_options *o)
+{
+	return error(ERRORMSG(o, would_overwrite), ce->name);
+}
+
+static int same(struct cache_entry *a, struct cache_entry *b)
+{
+	if (!!a != !!b)
+		return 0;
+	if (!a && !b)
+		return 1;
+	if ((a->ce_flags | b->ce_flags) & CE_CONFLICTED)
+		return 0;
+	return a->ce_mode == b->ce_mode &&
+	       !hashcmp(a->sha1, b->sha1);
+}
+
+
+/*
+ * When a CE gets turned into an unmerged entry, we
+ * want it to be up-to-date
+ */
+static int verify_uptodate_1(struct cache_entry *ce,
+				   struct unpack_trees_options *o,
+				   const char *error_msg)
+{
+	struct stat st;
+
+	if (o->index_only || (!((ce->ce_flags & CE_VALID) || ce_skip_worktree(ce)) && (o->reset || ce_uptodate(ce))))
+		return 0;
+
+	if (!lstat(ce->name, &st)) {
+		unsigned changed = ie_match_stat(o->src_index, ce, &st, CE_MATCH_IGNORE_VALID|CE_MATCH_IGNORE_SKIP_WORKTREE);
+		if (!changed)
+			return 0;
+		/*
+		 * NEEDSWORK: the current default policy is to allow
+		 * submodule to be out of sync wrt the supermodule
+		 * index.  This needs to be tightened later for
+		 * submodules that are marked to be automatically
+		 * checked out.
+		 */
+		if (S_ISGITLINK(ce->ce_mode))
+			return 0;
+		errno = 0;
+	}
+	if (errno == ENOENT)
+		return 0;
+	return o->gently ? -1 :
+		error(error_msg, ce->name);
+}
+
+static int verify_uptodate(struct cache_entry *ce,
+			   struct unpack_trees_options *o)
+{
+	if (!o->skip_sparse_checkout && will_have_skip_worktree(ce, o))
+		return 0;
+	return verify_uptodate_1(ce, o, ERRORMSG(o, not_uptodate_file));
+}
+
+static int verify_uptodate_sparse(struct cache_entry *ce,
+				  struct unpack_trees_options *o)
+{
+	return verify_uptodate_1(ce, o, ERRORMSG(o, sparse_not_uptodate_file));
+}
+
+static void invalidate_ce_path(struct cache_entry *ce, struct unpack_trees_options *o)
+{
+	if (ce)
+		cache_tree_invalidate_path(o->src_index->cache_tree, ce->name);
+}
+
+/*
+ * Check that checking out ce->sha1 in subdir ce->name is not
+ * going to overwrite any working files.
+ *
+ * Currently, git does not checkout subprojects during a superproject
+ * checkout, so it is not going to overwrite anything.
+ */
+static int verify_clean_submodule(struct cache_entry *ce, const char *action,
+				      struct unpack_trees_options *o)
+{
+	return 0;
+}
+
+static int verify_clean_subdirectory(struct cache_entry *ce, const char *action,
+				      struct unpack_trees_options *o)
+{
+	/*
+	 * we are about to extract "ce->name"; we would not want to lose
+	 * anything in the existing directory there.
+	 */
+	int namelen;
+	int i;
+	struct dir_struct d;
+	char *pathbuf;
+	int cnt = 0;
+	unsigned char sha1[20];
+
+	if (S_ISGITLINK(ce->ce_mode) &&
+	    resolve_gitlink_ref(ce->name, "HEAD", sha1) == 0) {
+		/* If we are not going to update the submodule, then
+		 * we don't care.
+		 */
+		if (!hashcmp(sha1, ce->sha1))
+			return 0;
+		return verify_clean_submodule(ce, action, o);
+	}
+
+	/*
+	 * First let's make sure we do not have a local modification
+	 * in that directory.
+	 */
+	namelen = strlen(ce->name);
+	for (i = locate_in_src_index(ce, o);
+	     i < o->src_index->cache_nr;
+	     i++) {
+		struct cache_entry *ce2 = o->src_index->cache[i];
+		int len = ce_namelen(ce2);
+		if (len < namelen ||
+		    strncmp(ce->name, ce2->name, namelen) ||
+		    ce2->name[namelen] != '/')
+			break;
+		/*
+		 * ce2->name is an entry in the subdirectory to be
+		 * removed.
+		 */
+		if (!ce_stage(ce2)) {
+			if (verify_uptodate(ce2, o))
+				return -1;
+			add_entry(o, ce2, CE_REMOVE, 0);
+			mark_ce_used(ce2, o);
+		}
+		cnt++;
+	}
+
+	/*
+	 * Then we need to make sure that we do not lose a locally
+	 * present file that is not ignored.
+	 */
+	pathbuf = xmalloc(namelen + 2);
+	memcpy(pathbuf, ce->name, namelen);
+	strcpy(pathbuf+namelen, "/");
+
+	memset(&d, 0, sizeof(d));
+	if (o->dir)
+		d.exclude_per_dir = o->dir->exclude_per_dir;
+	i = read_directory(&d, pathbuf, namelen+1, NULL);
+	if (i)
+		return o->gently ? -1 :
+			error(ERRORMSG(o, not_uptodate_dir), ce->name);
+	free(pathbuf);
+	return cnt;
+}
+
+/*
+ * This gets called when there was no index entry for the tree entry 'dst',
+ * but we found a file in the working tree that 'lstat()' said was fine,
+ * and we're on a case-insensitive filesystem.
+ *
+ * See if we can find a case-insensitive match in the index that also
+ * matches the stat information, and assume it's that other file!
+ */
+static int icase_exists(struct unpack_trees_options *o, struct cache_entry *dst, struct stat *st)
+{
+	struct cache_entry *src;
+
+	src = index_name_exists(o->src_index, dst->name, ce_namelen(dst), 1);
+	return src && !ie_match_stat(o->src_index, src, st, CE_MATCH_IGNORE_VALID|CE_MATCH_IGNORE_SKIP_WORKTREE);
+}
+
+/*
+ * We do not want to remove or overwrite a working tree file that
+ * is not tracked, unless it is ignored.
+ */
+static int verify_absent_1(struct cache_entry *ce, const char *action,
+				 struct unpack_trees_options *o,
+				 const char *error_msg)
+{
+	struct stat st;
+
+	if (o->index_only || o->reset || !o->update)
+		return 0;
+
+	if (has_symlink_or_noent_leading_path(ce->name, ce_namelen(ce)))
+		return 0;
+
+	if (!lstat(ce->name, &st)) {
+		int dtype = ce_to_dtype(ce);
+		struct cache_entry *result;
+
+		/*
+		 * It may be that the 'lstat()' succeeded even though
+		 * target 'ce' was absent, because there is an old
+		 * entry that is different only in case..
+		 *
+		 * Ignore that lstat() if it matches.
+		 */
+		if (ignore_case && icase_exists(o, ce, &st))
+			return 0;
+
+		if (o->dir && excluded(o->dir, ce->name, &dtype))
+			/*
+			 * ce->name is explicitly excluded, so it is Ok to
+			 * overwrite it.
+			 */
+			return 0;
+		if (S_ISDIR(st.st_mode)) {
+			/*
+			 * We are checking out path "foo" and
+			 * found "foo/." in the working tree.
+			 * This is tricky -- if we have modified
+			 * files that are in "foo/" we would lose
+			 * them.
+			 */
+			if (verify_clean_subdirectory(ce, action, o) < 0)
+				return -1;
+			return 0;
+		}
+
+		/*
+		 * The previous round may already have decided to
+		 * delete this path, which is in a subdirectory that
+		 * is being replaced with a blob.
+		 */
+		result = index_name_exists(&o->result, ce->name, ce_namelen(ce), 0);
+		if (result) {
+			if (result->ce_flags & CE_REMOVE)
+				return 0;
+		}
+
+		return o->gently ? -1 :
+			error(ERRORMSG(o, would_lose_untracked), ce->name, action);
+	}
+	return 0;
+}
+static int verify_absent(struct cache_entry *ce, const char *action,
+			 struct unpack_trees_options *o)
+{
+	if (!o->skip_sparse_checkout && will_have_skip_worktree(ce, o))
+		return 0;
+	return verify_absent_1(ce, action, o, ERRORMSG(o, would_lose_untracked));
+}
+
+static int verify_absent_sparse(struct cache_entry *ce, const char *action,
+			 struct unpack_trees_options *o)
+{
+	return verify_absent_1(ce, action, o, ERRORMSG(o, would_lose_orphaned));
+}
+
+static int merged_entry(struct cache_entry *merge, struct cache_entry *old,
+		struct unpack_trees_options *o)
+{
+	int update = CE_UPDATE;
+
+	if (!old) {
+		if (verify_absent(merge, "overwritten", o))
+			return -1;
+		invalidate_ce_path(merge, o);
+	} else if (!(old->ce_flags & CE_CONFLICTED)) {
+		/*
+		 * See if we can re-use the old CE directly?
+		 * That way we get the uptodate stat info.
+		 *
+		 * This also removes the UPDATE flag on a match; otherwise
+		 * we will end up overwriting local changes in the work tree.
+		 */
+		if (same(old, merge)) {
+			copy_cache_entry(merge, old);
+			update = 0;
+		} else {
+			if (verify_uptodate(old, o))
+				return -1;
+			if (ce_skip_worktree(old))
+				update |= CE_SKIP_WORKTREE;
+			invalidate_ce_path(old, o);
+		}
+	} else {
+		/*
+		 * Previously unmerged entry left as an existence
+		 * marker by read_index_unmerged();
+		 */
+		invalidate_ce_path(old, o);
+	}
+
+	add_entry(o, merge, update, CE_STAGEMASK);
+	return 1;
+}
+
+static int deleted_entry(struct cache_entry *ce, struct cache_entry *old,
+		struct unpack_trees_options *o)
+{
+	/* Did it exist in the index? */
+	if (!old) {
+		if (verify_absent(ce, "removed", o))
+			return -1;
+		return 0;
+	}
+	if (!(old->ce_flags & CE_CONFLICTED) && verify_uptodate(old, o))
+		return -1;
+	add_entry(o, ce, CE_REMOVE, 0);
+	invalidate_ce_path(ce, o);
+	return 1;
+}
+
+static int keep_entry(struct cache_entry *ce, struct unpack_trees_options *o)
+{
+	add_entry(o, ce, 0, 0);
+	return 1;
+}
+
+#if DBRT_DEBUG
+static void show_stage_entry(FILE *o,
+			     const char *label, const struct cache_entry *ce)
+{
+	if (!ce)
+		fprintf(o, "%s (missing)\n", label);
+	else
+		fprintf(o, "%s%06o %s %d\t%s\n",
+			label,
+			ce->ce_mode,
+			sha1_to_hex(ce->sha1),
+			ce_stage(ce),
+			ce->name);
+}
+#endif
+
+int threeway_merge(struct cache_entry **stages, struct unpack_trees_options *o)
+{
+	struct cache_entry *index;
+	struct cache_entry *head;
+	struct cache_entry *remote = stages[o->head_idx + 1];
+	int count;
+	int head_match = 0;
+	int remote_match = 0;
+
+	int df_conflict_head = 0;
+	int df_conflict_remote = 0;
+
+	int any_anc_missing = 0;
+	int no_anc_exists = 1;
+	int i;
+
+	for (i = 1; i < o->head_idx; i++) {
+		if (!stages[i] || stages[i] == o->df_conflict_entry)
+			any_anc_missing = 1;
+		else
+			no_anc_exists = 0;
+	}
+
+	index = stages[0];
+	head = stages[o->head_idx];
+
+	if (head == o->df_conflict_entry) {
+		df_conflict_head = 1;
+		head = NULL;
+	}
+
+	if (remote == o->df_conflict_entry) {
+		df_conflict_remote = 1;
+		remote = NULL;
+	}
+
+	/*
+	 * First, if there's a #16 situation, note that to prevent #13
+	 * and #14.
+	 */
+	if (!same(remote, head)) {
+		for (i = 1; i < o->head_idx; i++) {
+			if (same(stages[i], head)) {
+				head_match = i;
+			}
+			if (same(stages[i], remote)) {
+				remote_match = i;
+			}
+		}
+	}
+
+	/*
+	 * We start with cases where the index is allowed to match
+	 * something other than the head: #14(ALT) and #2ALT, where it
+	 * is permitted to match the result instead.
+	 */
+	/* #14, #14ALT, #2ALT */
+	if (remote && !df_conflict_head && head_match && !remote_match) {
+		if (index && !same(index, remote) && !same(index, head))
+			return o->gently ? -1 : reject_merge(index, o);
+		return merged_entry(remote, index, o);
+	}
+	/*
+	 * If we have an entry in the index cache, then we want to
+	 * make sure that it matches head.
+	 */
+	if (index && !same(index, head))
+		return o->gently ? -1 : reject_merge(index, o);
+
+	if (head) {
+		/* #5ALT, #15 */
+		if (same(head, remote))
+			return merged_entry(head, index, o);
+		/* #13, #3ALT */
+		if (!df_conflict_remote && remote_match && !head_match)
+			return merged_entry(head, index, o);
+	}
+
+	/* #1 */
+	if (!head && !remote && any_anc_missing)
+		return 0;
+
+	/*
+	 * Under the "aggressive" rule, we resolve mostly trivial
+	 * cases that we historically had git-merge-one-file resolve.
+	 */
+	if (o->aggressive) {
+		int head_deleted = !head;
+		int remote_deleted = !remote;
+		struct cache_entry *ce = NULL;
+
+		if (index)
+			ce = index;
+		else if (head)
+			ce = head;
+		else if (remote)
+			ce = remote;
+		else {
+			for (i = 1; i < o->head_idx; i++) {
+				if (stages[i] && stages[i] != o->df_conflict_entry) {
+					ce = stages[i];
+					break;
+				}
+			}
+		}
+
+		/*
+		 * Deleted in both.
+		 * Deleted in one and unchanged in the other.
+		 */
+		if ((head_deleted && remote_deleted) ||
+		    (head_deleted && remote && remote_match) ||
+		    (remote_deleted && head && head_match)) {
+			if (index)
+				return deleted_entry(index, index, o);
+			if (ce && !head_deleted) {
+				if (verify_absent(ce, "removed", o))
+					return -1;
+			}
+			return 0;
+		}
+		/*
+		 * Added in both, identically.
+		 */
+		if (no_anc_exists && head && remote && same(head, remote))
+			return merged_entry(head, index, o);
+
+	}
+
+	/* Below are "no merge" cases, which require that the index be
+	 * up-to-date to avoid the files getting overwritten with
+	 * conflict resolution files.
+	 */
+	if (index) {
+		if (verify_uptodate(index, o))
+			return -1;
+	}
+
+	o->nontrivial_merge = 1;
+
+	/* #2, #3, #4, #6, #7, #9, #10, #11. */
+	count = 0;
+	if (!head_match || !remote_match) {
+		for (i = 1; i < o->head_idx; i++) {
+			if (stages[i] && stages[i] != o->df_conflict_entry) {
+				keep_entry(stages[i], o);
+				count++;
+				break;
+			}
+		}
+	}
+#if DBRT_DEBUG
+	else {
+		fprintf(stderr, "read-tree: warning #16 detected\n");
+		show_stage_entry(stderr, "head   ", stages[head_match]);
+		show_stage_entry(stderr, "remote ", stages[remote_match]);
+	}
+#endif
+	if (head) { count += keep_entry(head, o); }
+	if (remote) { count += keep_entry(remote, o); }
+	return count;
+}
+
+/*
+ * Two-way merge.
+ *
+ * The rule is to "carry forward" what is in the index without losing
+ * information across a "fast-forward", favoring a successful merge
+ * over a merge failure when it makes sense.  For details of the
+ * "carry forward" rule, please see <Documentation/git-read-tree.txt>.
+ *
+ */
+int twoway_merge(struct cache_entry **src, struct unpack_trees_options *o)
+{
+	struct cache_entry *current = src[0];
+	struct cache_entry *oldtree = src[1];
+	struct cache_entry *newtree = src[2];
+
+	if (o->merge_size != 2)
+		return error("Cannot do a twoway merge of %d trees",
+			     o->merge_size);
+
+	if (oldtree == o->df_conflict_entry)
+		oldtree = NULL;
+	if (newtree == o->df_conflict_entry)
+		newtree = NULL;
+
+	if (current) {
+		if ((!oldtree && !newtree) || /* 4 and 5 */
+		    (!oldtree && newtree &&
+		     same(current, newtree)) || /* 6 and 7 */
+		    (oldtree && newtree &&
+		     same(oldtree, newtree)) || /* 14 and 15 */
+		    (oldtree && newtree &&
+		     !same(oldtree, newtree) && /* 18 and 19 */
+		     same(current, newtree))) {
+			return keep_entry(current, o);
+		}
+		else if (oldtree && !newtree && same(current, oldtree)) {
+			/* 10 or 11 */
+			return deleted_entry(oldtree, current, o);
+		}
+		else if (oldtree && newtree &&
+			 same(current, oldtree) && !same(current, newtree)) {
+			/* 20 or 21 */
+			return merged_entry(newtree, current, o);
+		}
+		else {
+			/* all other failures */
+			if (oldtree)
+				return o->gently ? -1 : reject_merge(oldtree, o);
+			if (current)
+				return o->gently ? -1 : reject_merge(current, o);
+			if (newtree)
+				return o->gently ? -1 : reject_merge(newtree, o);
+			return -1;
+		}
+	}
+	else if (newtree) {
+		if (oldtree && !o->initial_checkout) {
+			/*
+			 * deletion of the path was staged;
+			 */
+			if (same(oldtree, newtree))
+				return 1;
+			return reject_merge(oldtree, o);
+		}
+		return merged_entry(newtree, current, o);
+	}
+	return deleted_entry(oldtree, current, o);
+}
+
+/*
+ * Bind merge.
+ *
+ * Keep the index entries at stage0, collapse stage1 but make sure
+ * stage0 does not have anything there.
+ */
+int bind_merge(struct cache_entry **src,
+		struct unpack_trees_options *o)
+{
+	struct cache_entry *old = src[0];
+	struct cache_entry *a = src[1];
+
+	if (o->merge_size != 1)
+		return error("Cannot do a bind merge of %d trees\n",
+			     o->merge_size);
+	if (a && old)
+		return o->gently ? -1 :
+			error(ERRORMSG(o, bind_overlap), a->name, old->name);
+	if (!a)
+		return keep_entry(old, o);
+	else
+		return merged_entry(a, NULL, o);
+}
+
+/*
+ * One-way merge.
+ *
+ * The rule is:
+ * - take the stat information from stage0, take the data from stage1
+ */
+int oneway_merge(struct cache_entry **src, struct unpack_trees_options *o)
+{
+	struct cache_entry *old = src[0];
+	struct cache_entry *a = src[1];
+
+	if (o->merge_size != 1)
+		return error("Cannot do a oneway merge of %d trees",
+			     o->merge_size);
+
+	if (!a || a == o->df_conflict_entry)
+		return deleted_entry(old, old, o);
+
+	if (old && same(old, a)) {
+		int update = 0;
+		if (o->reset && !ce_uptodate(old) && !ce_skip_worktree(old)) {
+			struct stat st;
+			if (lstat(old->name, &st) ||
+			    ie_match_stat(o->src_index, old, &st, CE_MATCH_IGNORE_VALID|CE_MATCH_IGNORE_SKIP_WORKTREE))
+				update |= CE_UPDATE;
+		}
+		add_entry(o, old, update, 0);
+		return 0;
+	}
+	return merged_entry(a, old, o);
+}