patch: add longopts, --dry-run, add one more test

function                                             old     new   delta
patch_main                                          1110    1214    +104
static.patch_longopts                                  -      47     +47
packed_usage                                       26738   26761     +23
------------------------------------------------------------------------------
(add/remove: 1/0 grow/shrink: 2/0 up/down: 174/0)             Total: 174 bytes

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

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 */