backportpackage: fix automatic selection of the target release.

Signed-off-by: Mattia Rizzolo <mattia@debian.org>

backportpackage

@@ -29,7 +29,7 @@ from urllib.parse import quote
 
 import lsb_release
 from httplib2 import Http, HttpLib2Error
-from distro_info import DebianDistroInfo
+from distro_info import DebianDistroInfo, UbuntuDistroInfo
 
 from ubuntutools.archive import (DebianSourcePackage,
                                  UbuntuSourcePackage, DownloadError)
@@ -398,9 +398,15 @@ def main(args):
     if not opts.dest_releases:
         distinfo = lsb_release.get_distro_information()
         try:
-            opts.dest_releases = [distinfo['CODENAME']]
+            current_distro = distinfo['ID']
         except KeyError:
             error('No destination release specified and unable to guess yours.')
+        if current_distro == "Ubuntu":
+            opts.dest_releases = [UbuntuDistroInfo().lts()]
+        if current_distro == "Debian":
+            opts.dest_releases = [DebianDistroInfo().stable()]
+        else:
+            error(f"Unknown distribution {current_distro}, can't guess target release")
 
     if opts.workdir:
         workdir = os.path.expanduser(opts.workdir)

debian/changelog

@@ -10,6 +10,9 @@ ubuntu-dev-tools (0.187) UNRELEASED; urgency=medium
       Closes: #968316
   * backportpackage:
     + Support backporting to Debian releases.  LP: #974132
+    + Fix the guessing algorithm for the target release:
+      - for Debian: pick the current stable release.
+      - for Ubuntu: pick the current LTS release.
 
   [ Unit 193 ]
   * backportpackage: