feat(fastapi): add configurable commit hash display

Two new options have been added:

- [devel] commit_url
    - URL including an %s format specifier that can be used to link
      to a webpage for the commit.
- [devel] commit_hash
    - HEAD's commit hash (produced via `git rev-parse HEAD`)

If a `[devel] commit_hash` is configured, a link to the commit based on
`[devel] commit_url` will be displayed in the aurweb footer in
the form: `HEAD@<commit_hash>`. If no `[devel] commit_url` is
configured, a non-linked hash will be displayed.

Signed-off-by: Kevin Morris <kevr@0cost.org>

test/test_templates.py

@@ -1,6 +1,8 @@
 import pytest
 
+from aurweb import config, templates
 from aurweb.templates import register_filter, register_function
+from aurweb.testing.requests import Request
 
 
 @register_filter("func")
@@ -29,3 +31,42 @@ def test_register_function_exists_key_error():
         @register_function("function")
         def some_func():
             pass
+
+
+def test_commit_hash():
+    # Hashes we'll use for this test. long_commit_hash should be
+    # shortened to commit_hash for rendering.
+    commit_hash = "abcdefg"
+    long_commit_hash = commit_hash + "1234567"
+
+    def config_get_with_fallback(section: str, option: str,
+                                 fallback: str = None) -> str:
+        if section == "devel" and option == "commit_hash":
+            return long_commit_hash
+        return config.original_get_with_fallback(section, option, fallback)
+
+    # Fake config.get_with_fallback.
+    config.original_get_with_fallback = config.get_with_fallback
+    config.get_with_fallback = config_get_with_fallback
+
+    request = Request()
+    context = templates.make_context(request, "Test Context")
+    render = templates.render_raw_template(request, "index.html", context)
+
+    # We've faked config.get_with_fallback to return a "valid" commit_hash
+    # when queried. Test that the expected render occurs.
+    commit_url = config.get("devel", "commit_url")
+    expected = commit_url % commit_hash
+    assert expected in render
+    assert f"HEAD@{commit_hash}" in render
+    assert long_commit_hash not in render
+
+    # Restore config.get_with_fallback.
+    config.get_with_fallback = config.original_get_with_fallback
+    config.original_get_with_fallback = None
+
+    # Now, we no longer fake the commit_hash option: no commit
+    # is displayed in the footer. Assert this expectation.
+    context = templates.make_context(request, "Test Context")
+    render = templates.render_raw_template(request, "index.html", context)
+    assert commit_hash not in render