pmb.helpers.repo.urls: use channels.cfg mirrordirs (MR 1912)

Use mirrordir_pmos and mirrordir_alpine from channels.cfg to generate
the mirror URLs for postmarketOS and Alpine, which get written to
/etc/apk/repositories and which postmarketOS uses to download the
APKINDEX files.

Remove hardcoded "master" at the end of the postmarketOS mirror and use
mirrordir_pmos instead (which is "master" for the edge channel). Let the
postmarketOS mirror end in a '/' for consistency with the Alpine mirror
in pmb/config/__init__.py.

Remove obsolete --alpine-version. To experiment with a different Alpine
version, one should pass a custom --config-channels from now on.

test/test_helpers_repo.py

@@ -5,13 +5,15 @@ import pytest
 import sys
 
 import pmb_test  # noqa
+import pmb_test.const
 import pmb.helpers.repo
 
 
 @pytest.fixture
 def args(tmpdir, request):
     import pmb.parse
-    sys.argv = ["pmbootstrap.py", "chroot"]
+    cfg = f"{pmb_test.const.testdata}/channels.cfg"
+    sys.argv = ["pmbootstrap.py", "--config-channels", cfg, "chroot"]
     args = pmb.parse.arguments()
     args.log = args.work + "/log_testsuite.txt"
     pmb.helpers.logging.init(args)
@@ -30,3 +32,42 @@ def test_alpine_apkindex_path(args):
     args.mirror_alpine = "http://dl-cdn.alpinelinux.org/alpine/"
     ret = args.work + "/cache_apk_armhf/APKINDEX.30e6f5af.tar.gz"
     assert func(args, "testing", "armhf") == ret
+
+
+def test_urls(args, monkeypatch):
+    func = pmb.helpers.repo.urls
+    channel = "stable"
+    args.mirror_alpine = "http://localhost/alpine/"
+
+    # Second mirror with /master at the end is legacy, gets fixed by func.
+    # Note that bpo uses multiple postmarketOS mirrors at the same time, so it
+    # can use its WIP repository together with the final repository.
+    args.mirrors_postmarketos = ["http://localhost/pmos1/",
+                                 "http://localhost/pmos2/master"]
+
+    # Pretend to have a certain channel in pmaports.cfg
+    def read_config(args):
+        return {"channel": channel}
+    monkeypatch.setattr(pmb.config.pmaports, "read_config", read_config)
+
+    # Channel: stable
+    assert func(args) == ["/mnt/pmbootstrap-packages",
+                          "http://localhost/pmos1/v20.05",
+                          "http://localhost/pmos2/v20.05",
+                          "http://localhost/alpine/v3.11/main",
+                          "http://localhost/alpine/v3.11/community"]
+
+    # Channel: edge (has Alpine's testing)
+    channel = "edge"
+    assert func(args) == ["/mnt/pmbootstrap-packages",
+                          "http://localhost/pmos1/master",
+                          "http://localhost/pmos2/master",
+                          "http://localhost/alpine/edge/main",
+                          "http://localhost/alpine/edge/community",
+                          "http://localhost/alpine/edge/testing"]
+
+    # Only Alpine's URLs
+    exp = ["http://localhost/alpine/edge/main",
+           "http://localhost/alpine/edge/community",
+           "http://localhost/alpine/edge/testing"]
+    assert func(args, False, False) == exp