feature(keyringctl): use the export command purely to export keyrings

This gives more control over the export command that may be useful to
export a single packager to import it into gpg. This will also give more
flexibility to chain this function to the future verify stage.

By default the command exports the whole keyring directory.

keyringctl

@@ -1067,6 +1067,69 @@ def get_fingerprints(working_dir: Path, decomposed_paths: List[Path]) -> Set[Fin
     return fingerprints
 
 
+def export(
+    working_dir: Path,
+    keyring_root: Path,
+    sources: Optional[List[Path]] = None,
+    output: Optional[Path] = None,
+) -> str:
+    """Export all provided PGP packet files to a single output file
+
+    If sources contains directories, any .asc files below them are considered.
+
+    Parameters
+    ----------
+    working_dir: Path
+        A directory to use for temporary files
+    keyring_root: Path
+        The keyring root directory to look up username shorthand sources
+    sources: Optional[List[Path]]
+        A list of directories or files from which to read PGP packet information (defaults to `keyring_root`)
+    output: Optional[Path]
+        An output file that all PGP packet data is written to, return the result instead if None
+
+    Returns
+    -------
+    str
+        The result if no output file has been used
+    """
+
+    if not sources:
+        sources = [keyring_root]
+
+    # resolve shorthand username exports for packager keys
+    for index, source in enumerate(sources):
+        packager_source = keyring_root / "packager" / source.name
+        if not source.exists() and packager_source.exists():
+            sources[index] = packager_source
+
+    # depth first search certificate paths
+    cert_dirs: Set[Path] = set()
+    visit: List[Path] = sources
+    while visit:
+        path = visit.pop()
+        # this level contains a certificate, abort depth search
+        if list(path.glob("*.asc")):
+            cert_dirs.add(path)
+            continue
+        visit.extend([path for path in path.iterdir() if path.is_dir()])
+
+    temp_dir = Path(mkdtemp(dir=working_dir, prefix="arch-keyringctl-export-join-")).absolute()
+
+    certificates = []
+    for cert_dir in sorted(cert_dirs):
+        cert_path = temp_dir / f"{cert_dir.name}.asc"
+        debug(f"Joining {cert_dir} in {cert_path}")
+        packet_join(
+            packets=sorted(cert_dir.glob("**/*.asc")),
+            output=cert_path,
+            force=True,
+        )
+        certificates.append(cert_path)
+
+    return keyring_merge(certificates, output)
+
+
 def export_keyring(
     working_dir: Path,
     main: List[Path],
@@ -1194,30 +1257,13 @@ if __name__ == "__main__":
         "export",
         help="export a directory structure of PGP packet data to a combined file",
     )
-    export_parser.add_argument("output", type=absolute_path, help="file to write PGP packet data to")
+    export_parser.add_argument("-o", "--output", type=absolute_path, help="file to write PGP packet data to")
     export_parser.add_argument(
-        "-m",
-        "--main",
-        action="append",
-        help="files or directories containing PGP packet data that is trusted (can be provided multiple times)",
-        required=True,
+        "source",
+        nargs="*",
+        help="username or files/directories containing PGP packet data (can be provided multiple times)",
         type=absolute_path,
     )
-    export_parser.add_argument(
-        "-s",
-        "--source",
-        action="append",
-        help="files or directories containing PGP packet data (can be provided multiple times)",
-        required=True,
-        type=absolute_path,
-    )
-    export_parser.add_argument(
-        "-p",
-        "--pacman-integration",
-        action="store_true",
-        default=False,
-        help="export trusted and revoked files (used by pacman) alongside the keyring",
-    )
 
     args = parser.parse_args()
 
@@ -1257,13 +1303,14 @@ if __name__ == "__main__":
                     pacman_integration=True,
                 )
             elif "export" == args.subcommand:
-                export_keyring(
-                    working_dir=working_dir,
-                    main=args.main,
-                    sources=args.source,
-                    output=args.output,
-                    force=args.force,
-                    pacman_integration=args.pacman_integration,
+                print(
+                    export(
+                        working_dir=working_dir,
+                        keyring_root=keyring_root,
+                        sources=args.source,
+                        output=args.output,
+                    ),
+                    end="",
                 )
             else:
                 parser.print_help()