Allow setting the "all-features" setting in rust2rpm.conf

This new setting works the same way as the `--all-features` CLI flag
when set to `true`. This makes it possible to set it to `true` permanently,
without having to remember to use the CLI flag when running rust2rpm.

README.md

@@ -15,6 +15,9 @@ default settings (`[DEFAULT]`) and target-specific settings (i.e. `[fedora]`).
 
 These configuration options are available right now:
 
+- `all-features`: enable all cargo features when generating `BuildRequires`,
+  building the crate, and running cargo tests (defaults to `false`; setting this
+  value to `true` is equivalent to supplying the `--all-features` CLI flag)
 - `unwanted-features`: features or optional dependencies for which no
   `+feature` subpackage should be generated (for example, dependencies on Rust
   compiler internals for crates that are also bundled with Rust itself)

rust2rpm/__main__.py

@@ -412,7 +412,7 @@ def main():
     kwargs["generator_version"] = __version__
     kwargs["crate"] = crate
     kwargs["target"] = args.target
-    kwargs["all_features"] = args.all_features
+
     bins = [tgt for tgt in metadata.targets if tgt.kind == "bin"]
     libs = [tgt for tgt in metadata.targets if tgt.kind in {"lib", "rlib", "proc-macro"}]
     is_bin = len(bins) > 0
@@ -519,6 +519,13 @@ def main():
 
     kwargs["distconf"] = conf[args.target]
 
+    conf_all_features = conf[args.target].getboolean("all-features")
+    kwargs["all_features"] = conf_all_features or args.all_features
+
+    if conf_all_features is False and args.all_features:
+        print("WARNING: Conflicting settings for enabling all features: The setting is \"false\"")
+        print("         in rust2rpm.conf but it was enabled with the \"--all-features\" CLI flag.")
+
     spec_contents = template.render(md=metadata, patch_file=patch_file, **kwargs)
     if args.stdout:
         print(f"# {spec_file}")