fix(backup): detect the engine by its dump tool, not by the image name

36b2336 matched postgres and mariadb against the image's repository path. That name is not a property of the software: a dedicated Postgres inside an app's own stack is tagged <app>-database or postgis/postgis and carries no engine token at all, so it was never recognised, never dumped, and its data directory was copied as files without a single warning - the fallback notice hangs on found_db, which stayed false.

The container is now asked what it can run. pg_dumpall, mariadb-dump and mysqldump are probed by executing them, not by asking a shell for them, because a distroless image has no shell and would deny every tool it ships. The verdict is cached per image ID rather than per container, so replicas of one image cost a single probe.

Because the probe names the tool it found, the dump uses it instead of the hardcoded /usr/bin/mariadb-dump, which makes an image that ships only mysqldump dumpable rather than silently file-copied.

image_name and has_image are gone with their registry-host and tag stripping; the trap they worked around cannot occur when nothing reads the name. get_image_info stays, since the --images-* lists match exact references.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

src/baudolo/backup/docker.py

@@ -9,29 +9,25 @@ def get_image_info(container: str) -> str:
     )[0]
 
 
-def image_name(container: str) -> str:
-    """The image's repository path, without registry host, tag or digest.
+def image_id(container: str) -> str:
+    """The container's image ID, identical for every replica of one image."""
+    return execute_shell_command(
+        f"docker inspect --format '{{{{.Image}}}}' {container}"
+    )[0].strip()
 
-    A swarm node that hosts the local registry puts its own hostname in front
-    of every pull, so the raw reference of a Postgres container can read
-    `svc-db-mariadb-swarm-mgr-01:5000/postgres_custom:17-3.5`. Matching the
-    whole reference finds "mariadb" there and dumps the database with
-    mariadb-dump, which the Postgres image does not ship (exit 127). Tags bite
-    the same way: `xwiki_custom:lts-postgres-tomcat`.
+
+def has_tool(container: str, tool: str) -> bool:
+    """Whether *tool* runs inside the container.
+
+    Executes the binary rather than asking a shell for it: a distroless image
+    has no shell, and `sh -c 'command -v'` would answer "absent" for every
+    tool it ships.
     """
-    reference = get_image_info(container).strip().split("@", 1)[0]
-    head, _, tail = reference.rpartition("/")
-    tail = tail.split(":", 1)[0]
-    if head:
-        registry = head.split("/", 1)[0]
-        if "." in registry or ":" in registry or registry == "localhost":
-            head = head.partition("/")[2]
-    return f"{head}/{tail}" if head else tail
-
-
-def has_image(container: str, pattern: str) -> bool:
-    """Return True if the container's image name contains the pattern."""
-    return pattern in image_name(container)
+    try:
+        execute_shell_command(f"docker exec {container} {tool} --version")
+    except BackupException:
+        return False
+    return True
 
 
 def docker_volume_names() -> list[str]: