Add git shallow fetch test (#16055)

* add git shallow fetch test

covers https://github.com/ansible/ansible-modules-core/issues/3782

updating a repo with depth=1 fails silently if version==HEAD

* disable git shallow tests for old git versions

Older git versions don't treat the --depth option correctly.
While the git module tried to work around this and introduced subtle
bugs, ansible/ansible-modules-core#3794 falls back to full checkouts.
Don't run the tests then.

test/integration/roles/test_git/tasks/main.yml

@@ -19,6 +19,7 @@
 - name: set role facts
   set_fact:
     checkout_dir: '{{ output_dir }}/git'
+    repo_dir: '{{ output_dir }}/local_repos'
     repo_format1: 'https://github.com/jimi-c/test_role'
     repo_format2: 'git@github.com:jimi-c/test_role.git'
     repo_format3: 'ssh://git@github.com/jimi-c/test_role.git'
@@ -44,6 +45,11 @@
   shell: git --version | grep 'git version' | sed 's/git version //'
   register: git_version
 
+- name: set dummy git config
+  shell: git config --global user.email "noreply@example.com"; git config --global user.name "Ansible Test Runner"
+
+- name: create repo_dir
+  file: path={{repo_dir}} state=directory
 
 #
 # Test repo=https://github.com/...
@@ -595,6 +601,7 @@
     dest: '{{ checkout_dir }}'
     depth: 1
     version: master
+  when: git_version.stdout | version_compare("1.8.2", '>=')
 
 - name: switch to older branch with depth=1 (uses fetch)
   git:
@@ -603,10 +610,51 @@
     depth: 1
     version: earlybranch
   register: git_fetch
+  when: git_version.stdout | version_compare("1.8.2", '>=')
 
 - name: ensure the fetch succeeded
   assert:
     that: git_fetch|success
+  when: git_version.stdout | version_compare("1.8.2", '>=')
+
+- name: clear checkout_dir
+  file: state=absent path={{ checkout_dir }}
+
+# test for https://github.com/ansible/ansible-modules-core/issues/3782
+# make sure shallow fetch works when no version is specified
+
+- name: prepare old git repo
+  shell: git init; echo "1" > a; git add a; git commit -m "1"
+  args:
+    chdir: "{{repo_dir}}"
+
+- name: checkout old repo
+  git:
+    repo: '{{ repo_dir }}'
+    dest: '{{ checkout_dir }}'
+    depth: 1
+
+- name: "update repo"
+  shell: echo "2" > a; git commit -a -m "2"
+  args:
+    chdir: "{{repo_dir}}"
+
+- name: fetch updated repo
+  git:
+    repo: '{{ repo_dir }}'
+    dest: '{{ checkout_dir }}'
+    depth: 1
+  register: git_fetch
+  ignore_errors: yes
+
+- name: read file
+  shell: cat {{ checkout_dir }}/a
+
+- name: check update arrived
+  assert:
+    that:
+      - "{{ lookup('file', checkout_dir+'/a' )}} == 2"
+      - git_fetch|changed
 
 - name: clear checkout_dir
   file: state=absent path={{ checkout_dir }}