diff -r: avoid printing excess slashes in concatenated file names

* bootstrap.conf (gnulib_modules): Add filenamecat.
* src/diff.c: Include "filenamecat.h".
(compare_files): Use file_name_concat, rather than dir_file_pathname.
* src/util.c (dir_file_pathname): Remove now-unused function.
* src/diff.h: Remove its declaration.
* tests/excess-slash: New script to test for this.
* tests/Makefile.am (TESTS): Add it.
Forwarded by Santiago Vila from <bugs.debian.org/586301a>,
reported by Jari Aalto.

bootstrap.conf

@@ -33,6 +33,7 @@ extensions
 fcntl
 fdl
 file-type
+filenamecat
 fnmatch-gnu
 getopt
 gettext

gnulib

@@ -1 +1 @@
-Subproject commit 880f2b69df57af506439d6aaf1fe185a6f960e43
+Subproject commit 0c6cf5ab43555377b99d94febb2d6f23fc3d2cb0

src/diff.c

@@ -27,6 +27,7 @@
 #include <error.h>
 #include <exclude.h>
 #include <exitfail.h>
+#include <filenamecat.h>
 #include <file-type.h>
 #include <fnmatch.h>
 #include <getopt.h>
@@ -1067,9 +1068,9 @@ compare_files (struct comparison const *parent,
   else
     {
       cmp.file[0].name = free0
-	= dir_file_pathname (parent->file[0].name, name0);
+	= file_name_concat (parent->file[0].name, name0, NULL);
       cmp.file[1].name = free1
-	= dir_file_pathname (parent->file[1].name, name1);
+	= file_name_concat (parent->file[1].name, name1, NULL);
     }
 
   /* Stat the files.  */
@@ -1156,7 +1157,7 @@ compare_files (struct comparison const *parent,
       char const *fnm = cmp.file[fnm_arg].name;
       char const *dir = cmp.file[dir_arg].name;
       char const *filename = cmp.file[dir_arg].name = free0
-	= dir_file_pathname (dir, last_component (fnm));
+	= file_name_concat (dir, last_component (fnm), NULL);
 
       if (STREQ (fnm, "-"))
 	fatal ("cannot compare `-' to a directory");

src/diff.h

@@ -349,7 +349,6 @@ void print_sdiff_script (struct change *);
 extern char const change_letter[4];
 extern char const pr_program[];
 char *concat (char const *, char const *, char const *);
-char *dir_file_pathname (char const *, char const *);
 bool lines_differ (char const *, char const *);
 lin translate_line_number (struct file_data const *, lin);
 struct change *find_change (struct change *);

src/util.c

@@ -756,18 +756,6 @@ zalloc (size_t size)
   memset (p, 0, size);
   return p;
 }
-
-/* Yield the newly malloc'd pathname
-   of the file in DIR whose filename is FILE.  */
-
-char *
-dir_file_pathname (char const *dir, char const *file)
-{
-  char const *base = last_component (dir);
-  size_t baselen = base_len (base);
-  bool omit_slash = baselen == 0 || base[baselen - 1] == '/';
-  return concat (dir, "/" + omit_slash, file);
-}
 
 void
 debug_script (struct change *sp)

tests/Makefile.am

@@ -1,7 +1,8 @@
-TESTS = \
+jESTS = \
   basic \
   binary \
   colliding-file-names \
+  excess-slash \
   help-version	\
   function-line-vs-leading-space \
   label-vs-func	\

tests/excess-slash

@@ -0,0 +1,19 @@
+#!/bin/sh
+# Ensure that no excess slash appears in diff -r output.
+
+: ${srcdir=.}
+. "$srcdir/init.sh"; path_prepend_ ../src
+
+mkdir -p a/f b/f/g || framework_failure_
+echo Only in b/f: g > expected-out || framework_failure_
+
+fail=0
+
+diff -r a b/ > out 2> err && fail=1
+
+# expect no stderr
+compare err /dev/null || fail=1
+
+compare out expected-out || fail=1
+
+Exit $fail