patch --dry-run should not create or delete files.

2 files changed, 32 insertions, 3 deletions

diff --git a/tests/patch.test b/tests/patch.test
index 5cc60014..c18bfe1e 100755
--- a/tests/patch.test
+++ b/tests/patch.test
@@ -4,6 +4,14 @@
 
 #testing "name" "command" "result" "infile" "stdin"
 
+testing "dry run doesn't create file" \
+  "patch --dry-run >/dev/null && [ ! -e bork ] && echo yes" "yes\n" "" "
+--- /dev/null
++++ bork
+@@ -0,0 +1,1 @@
++one
+"
+
 testing "create file" "patch >/dev/null && cat bork" "one\ntwo\nthree\n" "" "
 --- /dev/null
 +++ bork
@@ -12,6 +20,7 @@ testing "create file" "patch >/dev/null && cat bork" "one\ntwo\nthree\n" "" "
 +two
 +three
 "
+
 testing "insert in middle" "patch > /dev/null && cat bork" \
   "one\nfour\ntwo\nthree\n" "" "
 --- bork
@@ -85,6 +94,23 @@ testing "quoted name" "patch > /dev/null && cat 'fruit bat'" \
 @@ -0,0 +1 @@
 +hello
 '
+
+testing "dry run doesn't delete file" \
+  "patch --dry-run > /dev/null && [ -e 'fruit bat' ] && echo yes" "yes\n" "" '
+--- "fruit bat"
++++ /dev/null
+@@ -1 +0,0 @@
+-hello
+'
+
+testing "delete file" \
+  "patch > /dev/null && [ ! -e 'fruit bat' ] && echo yes" "yes\n" "" '
+--- "fruit bat"
++++ /dev/null
+@@ -1 +0,0 @@
+-hello
+'
+
 # todo bork bork2
 
 # We hit a bug, test the bugfix.
diff --git a/toys/posix/patch.c b/toys/posix/patch.c
index 4b8c61c3..eebcddaa 100644
--- a/toys/posix/patch.c
+++ b/toys/posix/patch.c
@@ -449,7 +449,7 @@ void patch_main(void)
 
         if (del) {
           if (!FLAG(s)) printf("removing %s\n", name);
-          xunlink(name);
+          if (!FLAG(dry_run)) xunlink(name);
           state = 0;
         // If we've got a file to open, do so.
         } else if (!FLAG(p) || i <= TT.p) {
@@ -457,8 +457,11 @@ void patch_main(void)
           if ((!strcmp(oldname, "/dev/null") || !oldsum) && access(name, F_OK))
           {
             if (!FLAG(s)) printf("creating %s\n", name);
-            if (mkpath(name)) perror_exit("mkpath %s", name);
-            TT.filein = xcreate(name, O_CREAT|O_EXCL|O_RDWR, 0666);
+            if (FLAG(dry_run)) TT.filein = xopen("/dev/null", O_RDWR);
+            else {
+              if (mkpath(name)) perror_exit("mkpath %s", name);
+              TT.filein = xcreate(name, O_CREAT|O_EXCL|O_RDWR, 0666);
+            }
           } else {
             if (!FLAG(s)) printf("patching %s\n", name);
             TT.filein = xopenro(name);