[PATCH] Fix oversimplified optimization for add_cache_entry().

An earlier change to optimize directory-file conflict check
broke what "read-tree --emu23" expects.  This is fixed by this
commit.

(1) Introduces an explicit flag to tell add_cache_entry() not to
    check for conflicts and use it when reading an existing tree
    into an empty stage --- by definition this case can never
    introduce such conflicts.

(2) Makes read-cache.c:has_file_name() and read-cache.c:has_dir_name()
    aware of the cache stages, and flag conflict only with paths
    in the same stage.

Signed-off-by: Junio C Hamano <junkio@cox.net>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

cache.h

@@ -130,6 +130,7 @@ extern int write_cache(int newfd, struct cache_entry **cache, int entries);
 extern int cache_name_pos(const char *name, int namelen);
 #define ADD_CACHE_OK_TO_ADD 1		/* Ok to add */
 #define ADD_CACHE_OK_TO_REPLACE 2	/* Ok to replace file/directory */
+#define ADD_CACHE_SKIP_DFCHECK 4	/* Ok to skip DF conflict checks */
 extern int add_cache_entry(struct cache_entry *ce, int option);
 extern int remove_cache_entry_at(int pos);
 extern int remove_file_from_cache(char *path);

read-cache.c

@@ -179,6 +179,7 @@ static int has_file_name(const struct cache_entry *ce, int pos, int ok_to_replac
 {
 	int retval = 0;
 	int len = ce_namelen(ce);
+	int stage = ce_stage(ce);
 	const char *name = ce->name;
 
 	while (pos < active_nr) {
@@ -188,6 +189,8 @@ static int has_file_name(const struct cache_entry *ce, int pos, int ok_to_replac
 			break;
 		if (memcmp(name, p->name, len))
 			break;
+		if (ce_stage(p) != stage)
+			continue;
 		if (p->name[len] != '/')
 			continue;
 		retval = -1;
@@ -205,6 +208,7 @@ static int has_file_name(const struct cache_entry *ce, int pos, int ok_to_replac
 static int has_dir_name(const struct cache_entry *ce, int pos, int ok_to_replace)
 {
 	int retval = 0;
+	int stage = ce_stage(ce);
 	const char *name = ce->name;
 	const char *slash = name + ce_namelen(ce);
 
@@ -219,7 +223,7 @@ static int has_dir_name(const struct cache_entry *ce, int pos, int ok_to_replace
 		}
 		len = slash - name;
 
-		pos = cache_name_pos(name, len);
+		pos = cache_name_pos(name, ntohs(create_ce_flags(len, stage)));
 		if (pos >= 0) {
 			retval = -1;
 			if (ok_to_replace)
@@ -231,18 +235,23 @@ static int has_dir_name(const struct cache_entry *ce, int pos, int ok_to_replace
 		/*
 		 * Trivial optimization: if we find an entry that
 		 * already matches the sub-directory, then we know
-		 * we're ok, and we can exit
+		 * we're ok, and we can exit.
 		 */
 		pos = -pos-1;
-		if (pos < active_nr) {
+		while (pos < active_nr) {
 			struct cache_entry *p = active_cache[pos];
-			if (ce_namelen(p) <= len)
-				continue;
-			if (p->name[len] != '/')
-				continue;
-			if (memcmp(p->name, name, len))
-				continue;
-			break;
+			if ((ce_namelen(p) <= len) ||
+			    (p->name[len] != '/') ||
+			    memcmp(p->name, name, len))
+				break; /* not our subdirectory */
+			if (ce_stage(p) == stage)
+				/* p is at the same stage as our entry, and
+				 * is a subdirectory of what we are looking
+				 * at, so we cannot have conflicts at our
+				 * level or anything shorter.
+				 */
+				return retval;
+			pos++;
 		}
 	}
 	return retval;
@@ -277,6 +286,7 @@ int add_cache_entry(struct cache_entry *ce, int option)
 	int pos;
 	int ok_to_add = option & ADD_CACHE_OK_TO_ADD;
 	int ok_to_replace = option & ADD_CACHE_OK_TO_REPLACE;
+	int skip_df_check = option & ADD_CACHE_SKIP_DFCHECK;
 	pos = cache_name_pos(ce->name, ntohs(ce->ce_flags));
 
 	/* existing match? Just replace it */
@@ -302,7 +312,7 @@ int add_cache_entry(struct cache_entry *ce, int option)
 	if (!ok_to_add)
 		return -1;
 
-	if (!ce_stage(ce) && check_file_directory_conflict(ce, pos, ok_to_replace)) {
+	if (!skip_df_check && check_file_directory_conflict(ce, pos, ok_to_replace)) {
 		if (!ok_to_replace)
 			return -1;
 		pos = cache_name_pos(ce->name, ntohs(ce->ce_flags));

t/t1005-read-tree-m-2way-emu23.sh

@@ -366,6 +366,7 @@ test_expect_success \
      treeDF=`git-write-tree` &&
      echo treeDF $treeDF &&
      git-ls-tree $treeDF &&
+     git-ls-files --stage >DF.out
 
      rm -f DF &&
      mkdir DF &&
@@ -377,7 +378,7 @@ test_expect_success \
      git-ls-files --stage >DFDF.out'
 
 test_expect_success \
-    'DF vs DF/DF case test.' \
+    'DF vs DF/DF case test (#1)' \
     'rm -f .git/index &&
      rm -fr DF &&
      echo DF >DF &&
@@ -388,10 +389,24 @@ test_expect_success \
      check_cache_at DF/DF clean && # different from pure 2-way
      :'
 
+# The other way around
+test_expect_success \
+    'DF vs DF/DF case test (#2)' \
+    'rm -f .git/index &&
+     rm -fr DF &&
+     mkdir DF &&
+     echo DF/DF >DF/DF &&
+     git-update-cache --add DF/DF &&
+     read_tree_twoway $treeDFDF $treeDF &&
+     git-ls-files --stage >DFDFcheck.out &&
+     diff -u DF.out DFDFcheck.out &&
+     check_cache_at DF clean && # different from pure 2-way
+     :'
+
 # Emu23 can grok I having more than H.  Make sure we did not
-# botch the conflict tests (Linus code botches this test).
+# botch the conflict tests (fixed).
 test_expect_success \
-    'DF vs DF/DF case test (#2).' \
+    'DF vs DF/DF case test (#3).' \
     'rm -f .git/index &&
      rm -fr DF &&
      mkdir DF &&
@@ -400,8 +415,8 @@ test_expect_success \
      # This should fail because I and H have a conflict
      # at DF.
      if git-read-tree --emu23 $treeDF $treeDFDF
-     then true  ;# should be false
-     else false ;# should be true
+     then false
+     else true
      fi'
 
 test_done

tree.c

@@ -18,7 +18,7 @@ static int read_one_entry(unsigned char *sha1, const char *base, int baselen, co
 	memcpy(ce->name, base, baselen);
 	memcpy(ce->name + baselen, pathname, len+1);
 	memcpy(ce->sha1, sha1, 20);
-	return add_cache_entry(ce, ADD_CACHE_OK_TO_ADD);
+	return add_cache_entry(ce, ADD_CACHE_OK_TO_ADD|ADD_CACHE_SKIP_DFCHECK);
 }
 
 static int read_tree_recursive(void *buffer, unsigned long size,