1 files changed, 29 insertions, 6 deletions

diff --git a/editors/patch.c b/editors/patch.c
index 4a9715144..580ee147c 100644
--- a/editors/patch.c
+++ b/editors/patch.c
@@ -78,12 +78,23 @@ int patch_main(int argc UNUSED_PARAM, char **argv)
         enum {
                 OPT_R = (1 << 2),
                 OPT_N = (1 << 3),
+                OPT_dry_run = (1 << 4) * ENABLE_LONG_OPTS,
         };
 
         xfunc_error_retval = 2;
         {
                 const char *p = "-1";
                 const char *i = "-"; /* compat */
+#if ENABLE_LONG_OPTS
+                static const char patch_longopts[] ALIGN1 =
+                        "strip\0"   Required_argument "p"
+                        "input\0"   Required_argument "i"
+                        "reverse\0" No_argument       "R"
+                        "forward\0" No_argument       "N"
+                        "dry-run\0" No_argument       "\xff"
+                        ;
+                applet_long_options = patch_longopts;
+#endif
                 opt = getopt32(argv, "p:i:RN", &p, &i);
                 if (opt & OPT_R)
                         plus = '-';
@@ -97,7 +108,7 @@ int patch_main(int argc UNUSED_PARAM, char **argv)
                 FILE *dst_stream;
                 //char *old_filename;
                 char *new_filename;
-                char *backup_filename;
+                char *backup_filename = NULL;
                 unsigned src_cur_line = 1;
                 unsigned dst_cur_line = 0;
                 unsigned dst_beg_line;
@@ -131,16 +142,21 @@ int patch_main(int argc UNUSED_PARAM, char **argv)
                                 bb_make_directory(new_filename, -1, FILEUTILS_RECUR);
                                 *slash = '/';
                         }
-                        backup_filename = NULL;
                         src_stream = NULL;
                         saved_stat.st_mode = 0644;
-                } else {
+                } else if (!(opt & OPT_dry_run)) {
                         backup_filename = xasprintf("%s.orig", new_filename);
                         xrename(new_filename, backup_filename);
                         src_stream = xfopen_for_read(backup_filename);
+                } else
+                        src_stream = xfopen_for_read(new_filename);
+
+                if (opt & OPT_dry_run) {
+                        dst_stream = xfopen_for_write("/dev/null");
+                } else {
+                        dst_stream = xfopen_for_write(new_filename);
+                        fchmod(fileno(dst_stream), saved_stat.st_mode);
                 }
-                dst_stream = xfopen_for_write(new_filename);
-                fchmod(fileno(dst_stream), saved_stat.st_mode);
 
                 printf("patching file %s\n", new_filename);
 
@@ -189,6 +205,11 @@ int patch_main(int argc UNUSED_PARAM, char **argv)
                                 patch_line = xmalloc_fgets(patch_file);
                                 if (patch_line == NULL)
                                         break; /* EOF */
+                                if (!*patch_line) {
+                                        /* whitespace-damaged patch with "" lines */
+                                        free(patch_line);
+                                        patch_line = xstrdup(" ");
+                                }
                                 if ((*patch_line != '-') && (*patch_line != '+')
                                  && (*patch_line != ' ')
                                 ) {
@@ -244,7 +265,9 @@ int patch_main(int argc UNUSED_PARAM, char **argv)
                         if (backup_filename) {
                                 unlink(backup_filename);
                         }
-                        if ((dst_cur_line == 0) || (dst_beg_line == 0)) {
+                        if (!(opt & OPT_dry_run)
+                         && ((dst_cur_line == 0) || (dst_beg_line == 0))
+                        ) {
                                 /* The new patched file is empty, remove it */
                                 xunlink(new_filename);
                                 // /* old_filename and new_filename may be the same file */