dpkg-source: Improve warning message when ignoring file removals

Hint at the --include-removal option in the warning to direct the user
to it.

Closes: #738310

Signed-off-by: Guillem Jover <guillem@debian.org>

debian/changelog

@@ -27,6 +27,9 @@ dpkg (1.17.7) UNRELEASED; urgency=low
     Dpkg::Deps::deps_compare(). See: #737731
   * Clarify dpkg-genchanges error message on binary builds without any binary
     artifact built. Closes: #726520
+  * Improve dpkg-source warning message when ignoring file removals,
+    by adding a hint about the --include-removal option.
+    Thanks to Moritz Muehlenhoff <jmm@debian.org>. Closes: #738310
 
   [ Updated dpkg translations ]
   * German (Sven Joachim).

scripts/Dpkg/Source/Patch.pm

@@ -229,7 +229,7 @@ sub add_diff_directory {
                 push @diff_files, [$fn, 0, 0, "$old/$fn", '/dev/null',
                                    "$basedir.orig/$fn", '/dev/null'];
             } else {
-                warning(_g('ignoring deletion of file %s'), $fn);
+                warning(_g('ignoring deletion of file %s, use --include-removal to override'), $fn);
             }
         } elsif (-d _) {
             warning(_g('ignoring deletion of directory %s'), $fn);