Revert "Remove sylinked git cache functionality"

This reverts commit 9c1859c7f9.
For deployers having symlinks in the P branch, the removal of
those tasks would be problematic when doing an upgrade to Q.

Instead, we keep those tasks, and mention their deprecation.
People wanting to use the git cache can still use it, but
as a plain folder instead of a symlink.

Change-Id: Ief7ad423b9e701c145b97de42e5165fe2f7347d7

releasenotes/notes/deprecated-symlink-for-repo-cache-449b84e281ff9907.yaml

@@ -0,0 +1,12 @@
+---
+deprecations:
+  - |
+    In OSA deployments prior to Queens, if ``repo_git_cache_dir`` was set
+    to a folder which existed on a repo container host then that folder
+    would be symlinked to the repo container bind mount instead of
+    synchronising its contents to the repo container. This functionality
+    is deprecated in Queens and will be removed in Rocky. The ability to
+    make use of the git cache still exists, but the folder contents will
+    be synchronised from the deploy host to the repo container. If you
+    have made use of the symlink functionality previously, please move
+    the contents to a standard folder and remove the symlink.

tasks/repo_pre_install.yml

@@ -51,7 +51,6 @@
     group: "{{ repo_service_group_name }}"
     mode: "{{ item.mode | default('02755') }}"
   with_items:
-    - path: "{{ repo_git_cache_dir }}"
     - path: "{{ repo_service_home_folder }}"
     - path: "{{ repo_service_home_folder }}/.ssh"
       mode: "02700"
@@ -76,6 +75,23 @@
     owner: "root"
     group: "root"
 
+# TODO(evrardjp):
+# The functionality provided by the following two tasks is
+# deprecated in Queens and should be removed in Rocky. Apply
+# the changes as done in https://review.openstack.org/521750
+- name: Check if the git folder exists already
+  stat:
+    path: "{{ repo_git_cache_dir }}"
+  register: _git_folder
+
+- name: Git service data folder setup
+  file:
+    path: "{{ (_git_folder.stat.exists and _git_folder.stat.islnk) | ternary(_git_folder.stat.lnk_source, repo_git_cache_dir) }}"
+    state: "directory"
+    owner: "{{ repo_service_user_name }}"
+    group: "{{ repo_service_group_name }}"
+    recurse: true
+
 - name: File and directory setup (root user)
   file:
     path: "{{ item.path }}"