fix(changelog): allow rev range lookups without a tag format

The current default setting for `tag_format` is `None`. This is not a
problem for the `bump` command, since the `normalize_tag` function
defaults to `$version` when no `tag_format` is passed. However it is a
problem for the `changelog` command, which seems to explicitly demand a
`tag_format` in order to run a rev-range lookup. This creates issues
like #622.

Either a sane default needs to be set for `tag_format` or the
restriction in `changelog` has to be uplifted. In this commit the latter
has been chosen. A test is also implemented to check that `changelog`
will always compute a rev range with the default tag format.

Fixes #622

Author: gsalvatella

commitizen/commands/changelog.py

@@ -137,7 +137,7 @@ def __call__(self):
                 )
                 start_rev = self._find_incremental_rev(latest_tag_version, tags)
 
-        if self.rev_range and self.tag_format:
+        if self.rev_range:
             start_rev, end_rev = changelog.get_oldest_and_newest_rev(
                 tags,
                 version=self.rev_range,

tests/commands/test_changelog_command.py

@@ -659,6 +659,35 @@ def test_changelog_from_rev_single_version_not_found(
     assert "Could not find a valid revision" in str(excinfo)
 
 
+@pytest.mark.usefixtures("tmp_commitizen_project")
+@pytest.mark.freeze_time("2022-02-13")
+def test_changelog_from_rev_range_default_tag_format(mocker, config_path, changelog_path):
+    """Checks that rev_range is calculated with the default (None) tag format"""
+    # create commit and tag
+    create_file_and_commit("feat: new file")
+    testargs = ["cz", "bump", "--yes"]
+    mocker.patch.object(sys, "argv", testargs)
+    cli.main()
+    wait_for_tag()
+
+    create_file_and_commit("feat: after 0.2.0")
+    create_file_and_commit("feat: another feature")
+
+    testargs = ["cz", "bump", "--yes"]
+    mocker.patch.object(sys, "argv", testargs)
+    cli.main()
+    wait_for_tag()
+
+    testargs = ["cz", "changelog", "0.3.0"]
+    mocker.patch.object(sys, "argv", testargs)
+    cli.main()
+
+    with open(changelog_path, "r") as f:
+        out = f.read()
+
+    assert "new file" not in out
+
+
 @pytest.mark.usefixtures("tmp_commitizen_project")
 @pytest.mark.freeze_time("2022-02-13")
 def test_changelog_from_rev_range_version_not_found(mocker, config_path):