3 files changed, 82 insertions, 15 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 */
diff --git a/include/usage.h b/include/usage.h
index d03ec2295..85561c558 100644
--- a/include/usage.h
+++ b/include/usage.h
@@ -898,7 +898,7 @@
      "\n        -d      Daemonize" \
 
 #define dos2unix_trivial_usage \
-       "[OPTION] [FILE]"
+       "[OPTIONS] [FILE]"
 #define dos2unix_full_usage "\n\n" \
        "Convert FILE in-place from DOS to Unix format.\n" \
        "When no file is given, use stdin/stdout.\n" \
@@ -907,7 +907,7 @@
      "\n        -d      unix2dos" \
 
 #define unix2dos_trivial_usage \
-       "[OPTION] [FILE]"
+       "[OPTIONS] [FILE]"
 #define unix2dos_full_usage "\n\n" \
        "Convert FILE in-place from Unix to DOS format.\n" \
        "When no file is given, use stdin/stdout.\n" \
@@ -3250,12 +3250,21 @@
         )
 
 #define patch_trivial_usage \
-       "[-p NUM] [-i DIFF] [-R] [-N]"
+       "[OPTIONS] [ORIGFILE [PATCHFILE]]"
 #define patch_full_usage "\n\n" \
+        IF_LONG_OPTS( \
+       "        -p,--strip NUM  Strip NUM leading components from file names" \
+     "\n        -i,--input DIFF Read DIFF instead of stdin" \
+     "\n        -R,--reverse    Reverse patch" \
+     "\n        -N,--forward    Ignore already applied patches" \
+     "\n        --dry-run       Don't actually change files" \
+        ) \
+        IF_NOT_LONG_OPTS( \
        "        -p NUM  Strip NUM leading components from file names" \
      "\n        -i DIFF Read DIFF instead of stdin" \
      "\n        -R      Reverse patch" \
      "\n        -N      Ignore already applied patches" \
+        )
 
 #define patch_example_usage \
        "$ patch -p1 < example.diff\n" \
diff --git a/testsuite/patch.tests b/testsuite/patch.tests
index cfe69b76a..178048d2a 100755
--- a/testsuite/patch.tests
+++ b/testsuite/patch.tests
@@ -7,7 +7,7 @@
 # testing "test name" "options" "expected result" "file input" "stdin"
 
 testing "patch with old_file == new_file" \
-        "patch; echo $?; cat input" \
+        'patch; echo $?; cat input' \
 "\
 patching file input
 0
@@ -15,7 +15,10 @@ qwe
 asd
 zxc
 " \
-        "qwe\nzxc\n" \
+"\
+qwe
+zxc
+" \
 "\
 --- input       Jan 01 01:01:01 2000
 +++ input       Jan 01 01:01:01 2000
@@ -26,7 +29,7 @@ zxc
 " \
 
 testing "patch with nonexistent old_file" \
-        "patch; echo $?; cat input" \
+        'patch; echo $?; cat input' \
 "\
 patching file input
 0
@@ -34,7 +37,10 @@ qwe
 asd
 zxc
 " \
-        "qwe\nzxc\n" \
+"\
+qwe
+zxc
+" \
 "\
 --- input.doesnt_exist  Jan 01 01:01:01 2000
 +++ input       Jan 01 01:01:01 2000
@@ -45,14 +51,18 @@ zxc
 " \
 
 testing "patch -R with nonexistent old_file" \
-        "patch -R; echo $?; cat input" \
+        'patch -R; echo $?; cat input' \
 "\
 patching file input
 0
 qwe
 zxc
 " \
-        "qwe\nasd\nzxc\n" \
+"\
+qwe
+asd
+zxc
+" \
 "\
 --- input.doesnt_exist  Jan 01 01:01:01 2000
 +++ input       Jan 01 01:01:01 2000
@@ -62,4 +72,29 @@ zxc
  zxc
 " \
 
+testing "patch detects already applied hunk" \
+        'patch 2>&1; echo $?; cat input' \
+"\
+patching file input
+patch: hunk #1 FAILED at 1
+patch: 1 out of 1 hunk FAILED
+1
+abc
+def
+123
+" \
+"\
+abc
+def
+123
+" \
+"\
+--- input.old   Jan 01 01:01:01 2000
++++ input       Jan 01 01:01:01 2000
+@@ -1,2 +1,3 @@
+ abc
++def
+ 123
+" \
+
 exit $FAILCOUNT