Preserve extended attributes of patched files when possible

* src/patch.c (main): Set all file attributes of the temporary output
file before renaming it over the final output file (possibly replacing
the input file).  Pass the input file name to set_file_attributes().
* src/util.c (set_file_attributes): When enabled (USE_XATTR), also
copy extended attributes including attributes which define
permissions.
(copy_attr_error, copy_attr_quote, copy_attr_free, copy_attr_check,
copy_attr): Helper functions for copying extended attributes.
* m4/xattr.m4 (gl_FUNC_XATTR): Import from coreutils.
* src/Makefile.am (patch_LDADD): Add $(LIB_XATTR) here.
* bootstrap.conf: Use the gnulib verror module.

4 files changed, 76 insertions, 10 deletions

diff --git a/src/Makefile.am b/src/Makefile.am
index c1a1f9c..c119cfb 100644
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -31,7 +31,8 @@ patch_SOURCES = \
 	version.h
 
 AM_CPPFLAGS = -I$(top_builddir)/lib -I$(top_srcdir)/lib
-patch_LDADD = $(LDADD) $(top_builddir)/lib/libpatch.a $(LIB_CLOCK_GETTIME)
+patch_LDADD = $(LDADD) $(top_builddir)/lib/libpatch.a $(LIB_CLOCK_GETTIME) \
+	      $(LIB_XATTR)
 
 if ENABLE_MERGE
   patch_SOURCES += merge.c
diff --git a/src/patch.c b/src/patch.c
index 6d37581..77be499 100644
--- a/src/patch.c
+++ b/src/patch.c
@@ -476,9 +476,6 @@ main (int argc, char **argv)
 		      mode_t mode = file_type |
 			  ((new_mode ? new_mode : instat.st_mode) & S_IRWXUGO);
 
-		      move_file (TMPOUTNAME, &TMPOUTNAME_needs_removal, &outst,
-				 outname, mode, backup);
-
 		      if ((set_time | set_utc) && new_time.tv_sec != -1)
 			{
 			  struct timespec old_time = pch_timestamp (reverse);
@@ -500,7 +497,11 @@ main (int argc, char **argv)
 			}
 
 		      if (! inerrno)
-			set_file_attributes (outname, attr, &instat, mode, &new_time);
+			set_file_attributes (TMPOUTNAME, attr, inname, &instat,
+					     mode, &new_time);
+
+		      move_file (TMPOUTNAME, &TMPOUTNAME_needs_removal, &outst,
+				 outname, mode, backup);
 
 		      if (pch_rename ())
 		        {
diff --git a/src/util.c b/src/util.c
index 22b19d0..2f9c2f6 100644
--- a/src/util.c
+++ b/src/util.c
@@ -42,6 +42,13 @@
 #include <full-write.h>
 #include <tempname.h>
 
+#ifdef USE_XATTR
+# include <attr/error_context.h>
+# include <attr/libattr.h>
+# include <stdarg.h>
+# include "verror.h"
+#endif
+
 static void makedirs (char const *);
 
 typedef struct
@@ -123,9 +130,64 @@ contains_slash (const char *s)
   return false;
 }
 
+#ifdef USE_XATTR
+
+static void
+copy_attr_error (struct error_context *ctx, char const *fmt, ...)
+{
+  int err = errno;
+  va_list ap;
+
+  /* use verror module to print error message */
+  va_start (ap, fmt);
+  verror (0, err, fmt, ap);
+  va_end (ap);
+}
+
+static char const *
+copy_attr_quote (struct error_context *ctx, char const *str)
+{
+  return quotearg (str);
+}
+
+static void
+copy_attr_free (struct error_context *ctx, char const *str)
+{
+}
+
+static int
+copy_attr_check (const char *name, struct error_context *ctx)
+{
+	int action = attr_copy_action (name, ctx);
+	return action == 0 || action == ATTR_ACTION_PERMISSIONS;
+}
+
+static int
+copy_attr (char const *src_path, char const *dst_path)
+{
+  struct error_context ctx =
+  {
+    .error = copy_attr_error,
+    .quote = copy_attr_quote,
+    .quote_free = copy_attr_free
+  };
+  return attr_copy_file (src_path, dst_path, copy_attr_check, &ctx);
+}
+
+#else  /* USE_XATTR */
+
+static int
+copy_attr (char const *src_path, char const *dst_path)
+{
+  return 0;
+}
+
+#endif
+
 void
 set_file_attributes (char const *to, enum file_attributes attr,
-		     struct stat *st, mode_t mode, struct timespec *new_time)
+		     char const *from, struct stat *st, mode_t mode,
+		     struct timespec *new_time)
 {
   if (attr & FA_TIMES)
     {
@@ -170,6 +232,9 @@ set_file_attributes (char const *to, enum file_attributes attr,
 		S_ISLNK (st->st_mode) ? "symbolic link" : "file",
 		quotearg (to));
     }
+  if (copy_attr (from, to))
+    fatal_exit (0);
+  /* FIXME: There may be other attributes to preserve.  */
   if (attr & FA_MODE)
     {
 #if 0 && defined HAVE_LCHMOD
@@ -184,7 +249,6 @@ set_file_attributes (char const *to, enum file_attributes attr,
 		S_ISLNK (st->st_mode) ? "symbolic link" : "file",
 		quotearg (to));
     }
-  /* FIXME: There may be other attributes to preserve.  */
 }
 
 static void
@@ -196,7 +260,7 @@ create_backup_copy (char const *from, char const *to, struct stat *st,
 	     to_dir_known_to_exist);
   if (remember_backup)
     insert_file (&backup_st);
-  set_file_attributes (to, FA_TIMES | FA_IDS | FA_MODE, st, st->st_mode, NULL);
+  set_file_attributes (to, FA_TIMES | FA_IDS | FA_MODE, from, st, st->st_mode, NULL);
 }
 
 void
diff --git a/src/util.h b/src/util.h
index 521d098..6ab09f0 100644
--- a/src/util.h
+++ b/src/util.h
@@ -70,8 +70,8 @@ enum file_attributes {
   FA_MODE = 4
 };
 
-void set_file_attributes (char const *, enum file_attributes, struct stat *,
-			  mode_t, struct timespec *);
+void set_file_attributes (char const *, enum file_attributes, char const *,
+			  struct stat *, mode_t, struct timespec *);
 
 static inline char const *
 skip_spaces (char const *str)