Self-updates and program list from the repo

Catalog.py

@@ -0,0 +1,67 @@
+"""The program catalog: the Programs/ folder (manifests, templates, icons),
+fetched from the SaraSuite repo itself, so adding a program or fixing an
+install recipe only takes a push, not a new AppImage.
+
+The latest commit of the SaraSuite repo is checked the same way programs
+are (Sources.py). When it changed, its Programs/ folder is downloaded into
+~/.cache/SaraSuite/Catalog/. LoadPrograms() then reads that, falling back
+to the AppImage's bundled copy when there's no catalog yet, when it can't be
+loaded, or when running from source: there, the local Programs/ folder
+always wins, so unpushed manifest edits work while developing.
+"""
+
+import shutil
+from pathlib import Path
+from typing import Callable, Optional
+
+from Core import BundledManifestsDir, CacheHome, IsFrozen, LoadConfig
+from Sources import ClearDownloads, Download, LatestCommit, SourceError
+
+CatalogDir = CacheHome / "SaraSuite" / "Catalog"
+_CommitFile = CatalogDir / "Commit"
+_DownloadName = "SaraSuiteCatalog"
+
+
+def ManifestsDir() -> Path:
+    if IsFrozen and (CatalogDir / "Programs").is_dir():
+        return CatalogDir / "Programs"
+    return BundledManifestsDir
+
+
+def CatalogCommit() -> str:
+    return _CommitFile.read_text().strip() if _CommitFile.is_file() else ""
+
+
+def UpdateCatalog(Log: Optional[Callable[[str], None]] = None) -> bool:
+    """Fetch the SaraSuite repo's Programs/ if it has a new commit. Returns
+    True when the catalog changed (the program list should be reloaded).
+    Does nothing when running from source, and quietly keeps the current
+    catalog when the git host can't be reached."""
+    if not IsFrozen:
+        return False
+    Log = Log or (lambda Line: None)
+    Url = f"{LoadConfig().GitHost.rstrip('/')}/SaraSuite"
+    try:
+        Commit = LatestCommit(Url)
+    except SourceError:
+        return False
+    if Commit == CatalogCommit():
+        return False
+
+    try:
+        Source = Download(_DownloadName, Url, Commit, Log) / "Programs"
+        if not Source.is_dir():
+            return False
+        Staging = CatalogDir.with_name("Catalog.new")
+        shutil.rmtree(Staging, ignore_errors=True)
+        shutil.copytree(Source, Staging / "Programs", ignore=shutil.ignore_patterns("__pycache__"))
+        (Staging / "Commit").write_text(Commit)
+        shutil.rmtree(CatalogDir, ignore_errors=True)
+        Staging.rename(CatalogDir)
+    except (SourceError, OSError) as Error:
+        Log(f"Couldn't update the program list: {Error}")
+        return False
+    finally:
+        ClearDownloads(_DownloadName)
+    Log(f"Program list updated to SaraSuite commit {Commit[:7]}")
+    return True