libdpkg: Add virtual binary:Package field

This will allow printing package specifiers on query format strings.

Based-on-patch-by: Raphaël Hertzog <hertzog@debian.org>
Patch-sponsored-by: Linaro Limited

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

lib/dpkg/pkg-format.c

@@ -202,6 +202,14 @@ pkg_format_parse(const char *fmt)
 	return head;
 }
 
+static void
+virt_package(struct varbuf *vb,
+             const struct pkginfo *pkg, const struct pkgbin *pkgbin,
+             enum fwriteflags flags, const struct fieldinfo *fip)
+{
+	varbuf_add_pkgbin_name(vb, pkg, pkgbin, pnaw_nonambig);
+}
+
 static void
 virt_status_abbrev(struct varbuf *vb,
                    const struct pkginfo *pkg, const struct pkgbin *pkgbin,
@@ -274,6 +282,7 @@ virt_source_version(struct varbuf *vb,
 }
 
 const struct fieldinfo virtinfos[] = {
+	{ "binary:Package", NULL, virt_package },
 	{ "binary:Summary", NULL, virt_summary },
 	{ "db:Status-Abbrev", NULL, virt_status_abbrev },
 	{ "source:Package", NULL, virt_source_package },

man/dpkg-query.1

@@ -186,6 +186,7 @@ values from other fields (note that these do not use valid names for
 fields in control files):
 
 .nf
+    \fBbinary:Package\fP
     \fBbinary:Summary\fP
     \fBdb:Status\-Abbrev\fP
     \fBsource:Package\fP