read-tree -m -u: do not overwrite or remove untracked working tree files.

When a merge results in a creation of a path that did not exist
in HEAD, and if you already have that path on the working tree,
because the index has not been told about the working tree file,
read-tree happily removes it.  The issue was brought up by Santi
Béjar on the list.
Signed-off-by: NJunio C Hamano <junkio@cox.net>

read-tree.c

@@ -408,7 +408,7 @@ static void verify_uptodate(struct cache_entry *ce)
 {
 	struct stat st;
 
-	if (index_only)
+	if (index_only || reset)
 		return;
 
 	if (!lstat(ce->name, &st)) {
@@ -426,6 +426,21 @@ static void verify_uptodate(struct cache_entry *ce)
 	die("Entry '%s' not uptodate. Cannot merge.", ce->name);
 }
 
+/*
+ * We do not want to remove or overwrite a working tree file that
+ * is not tracked.
+ */
+static void verify_absent(const char *path, const char *action)
+{
+	struct stat st;
+
+	if (index_only || reset || !update)
+		return;
+	if (!lstat(path, &st))
+		die("Untracked working tree file '%s' "
+		    "would be %s by merge.", path, action);
+}
+
 static int merged_entry(struct cache_entry *merge, struct cache_entry *old)
 {
 	merge->ce_flags |= htons(CE_UPDATE);
@@ -443,6 +458,9 @@ static int merged_entry(struct cache_entry *merge, struct cache_entry *old)
 			verify_uptodate(old);
 		}
 	}
+	else
+		verify_absent(merge->name, "overwritten");
+
 	merge->ce_flags &= ~htons(CE_STAGEMASK);
 	add_cache_entry(merge, ADD_CACHE_OK_TO_ADD);
 	return 1;
@@ -452,6 +470,8 @@ static int deleted_entry(struct cache_entry *ce, struct cache_entry *old)
 {
 	if (old)
 		verify_uptodate(old);
+	else
+		verify_absent(ce->name, "removed");
 	ce->ce_mode = 0;
 	add_cache_entry(ce, ADD_CACHE_OK_TO_ADD);
 	return 1;
@@ -487,6 +507,7 @@ static int threeway_merge(struct cache_entry **stages)
 	int count;
 	int head_match = 0;
 	int remote_match = 0;
+	const char *path = NULL;
 
 	int df_conflict_head = 0;
 	int df_conflict_remote = 0;
@@ -498,8 +519,11 @@ static int threeway_merge(struct cache_entry **stages)
 	for (i = 1; i < head_idx; i++) {
 		if (!stages[i])
 			any_anc_missing = 1;
-		else
+		else {
+			if (!path)
+				path = stages[i]->name;
 			no_anc_exists = 0;
+		}
 	}
 
 	index = stages[0];
@@ -515,8 +539,15 @@ static int threeway_merge(struct cache_entry **stages)
 		remote = NULL;
 	}
 
+	if (!path && index)
+		path = index->name;
+	if (!path && head)
+		path = head->name;
+	if (!path && remote)
+		path = remote->name;
+
 	/* First, if there's a #16 situation, note that to prevent #13
-	 * and #14. 
+	 * and #14.
 	 */
 	if (!same(remote, head)) {
 		for (i = 1; i < head_idx; i++) {
@@ -575,6 +606,8 @@ static int threeway_merge(struct cache_entry **stages)
 		    (remote_deleted && head && head_match)) {
 			if (index)
 				return deleted_entry(index, index);
+			else if (path)
+				verify_absent(path, "removed");
 			return 0;
 		}
 		/*
@@ -592,6 +625,8 @@ static int threeway_merge(struct cache_entry **stages)
 	if (index) {
 		verify_uptodate(index);
 	}
+	else if (path)
+		verify_absent(path, "overwritten");
 
 	nontrivial_merge = 1;
 
@@ -689,7 +724,7 @@ static int oneway_merge(struct cache_entry **src)
 			     merge_size);
 
 	if (!a)
-		return deleted_entry(old, NULL);
+		return deleted_entry(old, old);
 	if (old && same(old, a)) {
 		if (reset) {
 			struct stat st;
@@ -699,7 +734,7 @@ static int oneway_merge(struct cache_entry **src)
 		}
 		return keep_entry(old);
 	}
-	return merged_entry(a, NULL);
+	return merged_entry(a, old);
 }
 
 static int read_cache_unmerged(void)

t/t1002-read-tree-m-u-2way.sh

@@ -39,7 +39,6 @@ test_expect_success \
      echo nitfol >nitfol &&
      echo bozbar >bozbar &&
      echo rezrov >rezrov &&
-     echo yomin >yomin &&
      git-update-index --add nitfol bozbar rezrov &&
      treeH=`git-write-tree` &&
      echo treeH $treeH &&
@@ -56,7 +55,8 @@ test_expect_success \
 
 test_expect_success \
     '1, 2, 3 - no carry forward' \
-    'rm -f .git/index &&
+    'rm -f .git/index nitfol bozbar rezrov frotz &&
+     git-read-tree --reset -u $treeH &&
      git-read-tree -m -u $treeH $treeM &&
      git-ls-files --stage >1-3.out &&
      cmp M.out 1-3.out &&
@@ -66,11 +66,12 @@ test_expect_success \
      check_cache_at frotz clean &&
      check_cache_at nitfol clean'
 
-echo '+100644 X 0	yomin' >expected
-
 test_expect_success \
     '4 - carry forward local addition.' \
-    'rm -f .git/index &&
+    'rm -f .git/index nitfol bozbar rezrov frotz &&
+     git-read-tree --reset -u $treeH &&
+     echo "+100644 X 0	yomin" >expected &&
+     echo yomin >yomin &&
      git-update-index --add yomin &&
      git-read-tree -m -u $treeH $treeM &&
      git-ls-files --stage >4.out || return 1
@@ -85,7 +86,9 @@ test_expect_success \
 
 test_expect_success \
     '5 - carry forward local addition.' \
-    'rm -f .git/index &&
+    'rm -f .git/index nitfol bozbar rezrov frotz &&
+     git-read-tree --reset -u $treeH &&
+     git-read-tree -m -u $treeH &&
      echo yomin >yomin &&
      git-update-index --add yomin &&
      echo yomin yomin >yomin &&
@@ -103,7 +106,9 @@ test_expect_success \
 
 test_expect_success \
     '6 - local addition already has the same.' \
-    'rm -f .git/index &&
+    'rm -f .git/index nitfol bozbar rezrov frotz &&
+     git-read-tree --reset -u $treeH &&
+     echo frotz >frotz &&
      git-update-index --add frotz &&
      git-read-tree -m -u $treeH $treeM &&
      git-ls-files --stage >6.out &&
@@ -117,7 +122,8 @@ test_expect_success \
 
 test_expect_success \
     '7 - local addition already has the same.' \
-    'rm -f .git/index &&
+    'rm -f .git/index nitfol bozbar rezrov frotz &&
+     git-read-tree --reset -u $treeH &&
      echo frotz >frotz &&
      git-update-index --add frotz &&
      echo frotz frotz >frotz &&
@@ -134,14 +140,16 @@ test_expect_success \
 
 test_expect_success \
     '8 - conflicting addition.' \
-    'rm -f .git/index &&
+    'rm -f .git/index nitfol bozbar rezrov frotz &&
+     git-read-tree --reset -u $treeH &&
      echo frotz frotz >frotz &&
      git-update-index --add frotz &&
      if git-read-tree -m -u $treeH $treeM; then false; else :; fi'
 
 test_expect_success \
     '9 - conflicting addition.' \
-    'rm -f .git/index &&
+    'rm -f .git/index nitfol bozbar rezrov frotz &&
+     git-read-tree --reset -u $treeH &&
      echo frotz frotz >frotz &&
      git-update-index --add frotz &&
      echo frotz >frotz &&
@@ -149,7 +157,8 @@ test_expect_success \
 
 test_expect_success \
     '10 - path removed.' \
-    'rm -f .git/index &&
+    'rm -f .git/index nitfol bozbar rezrov frotz &&
+     git-read-tree --reset -u $treeH &&
      echo rezrov >rezrov &&
      git-update-index --add rezrov &&
      git-read-tree -m -u $treeH $treeM &&
@@ -160,7 +169,8 @@ test_expect_success \
 
 test_expect_success \
     '11 - dirty path removed.' \
-    'rm -f .git/index &&
+    'rm -f .git/index nitfol bozbar rezrov frotz &&
+     git-read-tree --reset -u $treeH &&
      echo rezrov >rezrov &&
      git-update-index --add rezrov &&
      echo rezrov rezrov >rezrov &&
@@ -168,14 +178,16 @@ test_expect_success \
 
 test_expect_success \
     '12 - unmatching local changes being removed.' \
-    'rm -f .git/index &&
+    'rm -f .git/index nitfol bozbar rezrov frotz &&
+     git-read-tree --reset -u $treeH &&
      echo rezrov rezrov >rezrov &&
      git-update-index --add rezrov &&
      if git-read-tree -m -u $treeH $treeM; then false; else :; fi'
 
 test_expect_success \
     '13 - unmatching local changes being removed.' \
-    'rm -f .git/index &&
+    'rm -f .git/index nitfol bozbar rezrov frotz &&
+     git-read-tree --reset -u $treeH &&
      echo rezrov rezrov >rezrov &&
      git-update-index --add rezrov &&
      echo rezrov >rezrov &&
@@ -188,7 +200,8 @@ EOF
 
 test_expect_success \
     '14 - unchanged in two heads.' \
-    'rm -f .git/index &&
+    'rm -f .git/index nitfol bozbar rezrov frotz &&
+     git-read-tree --reset -u $treeH &&
      echo nitfol nitfol >nitfol &&
      git-update-index --add nitfol &&
      git-read-tree -m -u $treeH $treeM &&
@@ -207,7 +220,8 @@ test_expect_success \
 
 test_expect_success \
     '15 - unchanged in two heads.' \
-    'rm -f .git/index &&
+    'rm -f .git/index nitfol bozbar rezrov frotz &&
+     git-read-tree --reset -u $treeH &&
      echo nitfol nitfol >nitfol &&
      git-update-index --add nitfol &&
      echo nitfol nitfol nitfol >nitfol &&
@@ -227,14 +241,16 @@ test_expect_success \
 
 test_expect_success \
     '16 - conflicting local change.' \
-    'rm -f .git/index &&
+    'rm -f .git/index nitfol bozbar rezrov frotz &&
+     git-read-tree --reset -u $treeH &&
      echo bozbar bozbar >bozbar &&
      git-update-index --add bozbar &&
      if git-read-tree -m -u $treeH $treeM; then false; else :; fi'
 
 test_expect_success \
     '17 - conflicting local change.' \
-    'rm -f .git/index &&
+    'rm -f .git/index nitfol bozbar rezrov frotz &&
+     git-read-tree --reset -u $treeH &&
      echo bozbar bozbar >bozbar &&
      git-update-index --add bozbar &&
      echo bozbar bozbar bozbar >bozbar &&
@@ -242,7 +258,8 @@ test_expect_success \
 
 test_expect_success \
     '18 - local change already having a good result.' \
-    'rm -f .git/index &&
+    'rm -f .git/index nitfol bozbar rezrov frotz &&
+     git-read-tree --reset -u $treeH &&
      echo gnusto >bozbar &&
      git-update-index --add bozbar &&
      git-read-tree -m -u $treeH $treeM &&
@@ -254,7 +271,8 @@ test_expect_success \
 
 test_expect_success \
     '19 - local change already having a good result, further modified.' \
-    'rm -f .git/index &&
+    'rm -f .git/index nitfol bozbar rezrov frotz &&
+     git-read-tree --reset -u $treeH &&
      echo gnusto >bozbar &&
      git-update-index --add bozbar &&
      echo gnusto gnusto >bozbar &&
@@ -273,7 +291,8 @@ test_expect_success \
 
 test_expect_success \
     '20 - no local change, use new tree.' \
-    'rm -f .git/index &&
+    'rm -f .git/index nitfol bozbar rezrov frotz &&
+     git-read-tree --reset -u $treeH &&
      echo bozbar >bozbar &&
      git-update-index --add bozbar &&
      git-read-tree -m -u $treeH $treeM &&
@@ -285,7 +304,8 @@ test_expect_success \
 
 test_expect_success \
     '21 - no local change, dirty cache.' \
-    'rm -f .git/index &&
+    'rm -f .git/index nitfol bozbar rezrov frotz &&
+     git-read-tree --reset -u $treeH &&
      echo bozbar >bozbar &&
      git-update-index --add bozbar &&
      echo gnusto gnusto >bozbar &&
@@ -294,7 +314,7 @@ test_expect_success \
 # Also make sure we did not break DF vs DF/DF case.
 test_expect_success \
     'DF vs DF/DF case setup.' \
-    'rm -f .git/index &&
+    'rm -f .git/index
      echo DF >DF &&
      git-update-index --add DF &&
      treeDF=`git-write-tree` &&

t/t3500-cherry.sh

@@ -30,6 +30,7 @@ test_expect_success \
      git-commit -m "Add C." &&
 
      git-checkout -f master &&
+     rm -f B C &&
 
      echo Third >> A &&
      git-update-index A &&

t/t4002-diff-basic.sh

@@ -191,7 +191,7 @@ test_expect_success \
     'rm -fr Z [A-Z][A-Z] &&
      git-read-tree $tree_A &&
      git-checkout-index -f -a &&
-     git-read-tree -m $tree_O || return 1
+     git-read-tree --reset $tree_O || return 1
      git-update-index --refresh >/dev/null ;# this can exit non-zero
      git-diff-files >.test-a &&
      cmp_diff_files_output .test-a .test-recursive-OA'
@@ -201,7 +201,7 @@ test_expect_success \
     'rm -fr Z [A-Z][A-Z] &&
      git-read-tree $tree_B &&
      git-checkout-index -f -a &&
-     git-read-tree -m $tree_O || return 1
+     git-read-tree --reset $tree_O || return 1
      git-update-index --refresh >/dev/null ;# this can exit non-zero
      git-diff-files >.test-a &&
      cmp_diff_files_output .test-a .test-recursive-OB'
@@ -211,7 +211,7 @@ test_expect_success \
     'rm -fr Z [A-Z][A-Z] &&
      git-read-tree $tree_B &&
      git-checkout-index -f -a &&
-     git-read-tree -m $tree_A || return 1
+     git-read-tree --reset $tree_A || return 1
      git-update-index --refresh >/dev/null ;# this can exit non-zero
      git-diff-files >.test-a &&
      cmp_diff_files_output .test-a .test-recursive-AB'

t/t6022-merge-rename.sh

@@ -111,6 +111,7 @@ test_expect_success 'pull renaming branch into unrenaming one' \
 
 test_expect_success 'pull renaming branch into another renaming one' \
 '
+	rm -f B
 	git reset --hard
 	git checkout red
 	git pull . white && {