Dpkg::Source::Package::V3::git::do_build(): remove extra quotes

Remove extra quoting that should not be there while passing an exclude
file to git ls-files during build of 3.0 (git) source package.

Based-on-patch-by: Courtney Bane <debian-bugs-5265@cbane.org>

debian/changelog

@@ -69,6 +69,9 @@ dpkg (1.15.5) UNRELEASED; urgency=low
     dpkg-dev → xz-utils to ensure xz and unxz are available.
   * Fix dpkg-source --include-binaries to correctly compute the path name of
     the discovered binary files. Closes: #554612
+  * Remove extra quoting that should not be there while passing an exclude
+    file to git ls-files during build of 3.0 (git) source package.
+    Thanks to Courtney Bane for the patch. Closes: #551829
 
   [ Updated dpkg translations ]
   * Czech (Miroslav Kure).

scripts/Dpkg/Source/Package/V3/git.pm

@@ -145,7 +145,7 @@ sub do_build {
     my $core_excludesfile = `git config --get core.excludesfile`;
     chomp $core_excludesfile;
     if (length $core_excludesfile && -e $core_excludesfile) {
-	push @ignores, "--exclude-from='$core_excludesfile'";
+	push @ignores, "--exclude-from=$core_excludesfile";
     }
     if (-e ".git/info/exclude") {
 	push @ignores, "--exclude-from=.git/info/exclude";