cli: convert docker-build tag auto to semver2

closes #414

reana/reana_dev/docker.py

@@ -32,7 +32,7 @@ def docker_commands():
     default="latest",
     help="Image tag to generate. Default 'latest'. "
     "Use 'auto' to generate git-tag-based value such as "
-    "'0.5.1-3-g75ae5ce'",
+    "'0.7.0-alpha.3'",
 )
 @click.option(
     "--component",
@@ -100,7 +100,7 @@ def docker_build(
     :param exclude_components: List of components to exclude from the build.
     :param user: DockerHub organisation or user name. [default=reanahub]
     :param tag: Docker image tag to generate. Default 'latest'.  Use 'auto' to
-        generate git-tag-based value such as '0.5.1-3-g75ae5ce'.
+        generate git-tag-based value such as '0.7.0-alpha.3'.
     :param build_arg: Optional docker build argument. (e.g. DEBUG=1)
     :param no_cache: Flag instructing to avoid using cache. [default=False]
     :param output_component_versions: File where to write the built images
@@ -209,7 +209,7 @@ def docker_rmi(user, tag, component):  # noqa: D301
     default="latest",
     help="Image tag to push. Default 'latest'. "
     "Use 'auto' to push git-tag-based value such as "
-    "'0.5.1-3-g75ae5ce'",
+    "'0.7.0-alpha.3'",
 )
 @click.option(
     "--component",
@@ -240,7 +240,7 @@ def docker_push(user, tag, component):  # noqa: D301
                                all REANA repositories.
     :param user: DockerHub organisation or user name. [default=reanahub]
     :param tag: Docker image tag to push. Default 'latest'.  Use 'auto' to
-        push git-tag-based value such as '0.5.1-3-g75ae5ce'.
+        push git-tag-based value such as '0.7.0-alpha.3'.
     :param tag: Docker tag to use. [default=latest]
     :type component: str
     :type user: str

reana/reana_dev/release.py

@@ -26,10 +26,8 @@
     get_current_component_version_from_source_files,
     get_current_tag,
     is_component_dockerised,
-    parse_pep440_version,
     run_command,
     select_components,
-    translate_pep440_to_semver2,
 )
 
 
@@ -111,23 +109,8 @@ def release_docker(ctx, component, user, image_name):  # noqa: D301
         if not is_component_dockerised(component_):
             cannot_release_on_dockerhub.append(component_)
         is_component_releasable(component_, exit_code=True, display=True)
-
-        current_tag = get_current_tag(component_)
         full_image_name = f"{user}/{image_name or component_}"
-        docker_tag = ""
-
-        if parse_pep440_version(current_tag):
-            docker_tag = translate_pep440_to_semver2(current_tag)
-        elif semver.VersionInfo.isvalid(current_tag):
-            docker_tag = current_tag
-        else:
-            display_message(
-                f"The component's latest tag ({current_tag}) is not a "
-                "valid version (nor PEP440 nor semver2 compliant).",
-                component_,
-            )
-            sys.exit(1)
-
+        docker_tag = get_current_tag(component_)
         run_command(
             f"docker tag {full_image_name}:latest {full_image_name}:{docker_tag}",
             component_,

reana/reana_dev/utils.py

@@ -707,7 +707,7 @@ def bump_component_version(component, current_version, next_version=None):
         )
 
 
-def get_current_tag(component):
+def get_git_tag(component):
     """Return the current version of a component.
 
     :param component: standard component name
@@ -724,3 +724,24 @@ def validate_mode_option(ctx, param, value):
             "Supported values are '{}'.".format("', '".join(CLUSTER_DEPLOYMENT_MODES))
         )
     return value
+
+
+def get_current_tag(component):
+    """Return the current semver version of a component.
+
+    :param component: standard component name
+    :type component: str
+    """
+    tag = get_git_tag(component)
+
+    if parse_pep440_version(tag):
+        return translate_pep440_to_semver2(tag)
+    elif semver.VersionInfo.isvalid(tag):
+        return tag
+    else:
+        display_message(
+            f"The component's latest tag ({tag}) is not a "
+            "valid version (nor PEP440 nor semver2 compliant).",
+            component,
+        )
+        sys.exit(1)