Ignore access mode when merging volumes short syntax

The target path inside the container is treated as a key. Ref:
https://github.com/compose-spec/compose-spec/blob/master/spec.md#merging-service-definitions

Signed-off-by: Bhavin Gandhi <bhavin7392@gmail.com>

podman_compose.py

@@ -1315,11 +1315,11 @@ def rec_merge_one(target, source):
         if is_list(value2):
             if key == "volumes":
                 # clean duplicate mount targets
-                pts = {v.split(":", 1)[1] for v in value2 if ":" in v}
+                pts = {v.split(":", 2)[1] for v in value2 if ":" in v}
                 del_ls = [
                     ix
                     for (ix, v) in enumerate(value)
-                    if ":" in v and v.split(":", 1)[1] in pts
+                    if ":" in v and v.split(":", 2)[1] in pts
                 ]
                 for ix in reversed(del_ls):
                     del value[ix]

tests/volumes_merge/docker-compose.override.yaml

@@ -0,0 +1,7 @@
+version: "3"
+services:
+  web:
+    volumes:
+      - ./override.txt:/var/www/html/index.html:ro,z
+      - ./override.txt:/var/www/html/index2.html:z
+      - ./override.txt:/var/www/html/index3.html

tests/volumes_merge/docker-compose.yaml

@@ -0,0 +1,11 @@
+version: "3"
+services:
+  web:
+    image: busybox
+    command: ["/bin/busybox", "httpd", "-f", "-h", "/var/www/html", "-p", "8080"]
+    ports:
+      - 8080:8080
+    volumes:
+      - ./index.txt:/var/www/html/index.html:ro,z
+      - ./index.txt:/var/www/html/index2.html
+      - ./index.txt:/var/www/html/index3.html:ro

tests/volumes_merge/index.txt

@@ -0,0 +1 @@
+The file from docker-compose.yaml

tests/volumes_merge/override.txt

@@ -0,0 +1 @@
+The file from docker-compose.override.yaml