[PATCH 3/8] bootlinux: add git ref verification before cloning

[Luis Chamberlain <mcgrof@kernel.org>]

Add preliminary verification tasks to check if the target git ref exists
before attempting to clone the Linux kernel repository. This prevents
confusing git clone failures and provides clear, actionable error messages
to users.

The verification is particularly important for A/B testing scenarios where:
- Different kernel refs may be used for baseline vs development builds
- Shallow clones might not contain all required refs
- Users may specify refs that don't exist in the repository

Each build method now verifies the ref availability:
- 9p.yml: Verifies active_linux_ref (or target_linux_ref fallback)
- targets.yml: Verifies target_linux_ref on target nodes
- builder.yml: Verifies target_linux_ref on builder nodes

The error messages guide users to:
1. Check if the ref actually exists in the repository
2. Disable shallow cloning when using A/B testing with different refs
3. Verify the repository URL is correct and accessible

This change improves the user experience by failing fast with helpful
diagnostics rather than letting git clone fail with cryptic errors.

Generated-by: Claude AI
Signed-off-by: Luis Chamberlain <mcgrof@kernel.org>
---
 playbooks/roles/bootlinux/tasks/build/9p.yml  | 29 +++++++++++++++++++
 .../roles/bootlinux/tasks/build/builder.yml   | 21 ++++++++++++++
 .../roles/bootlinux/tasks/build/targets.yml   | 22 ++++++++++++++
 3 files changed, 72 insertions(+)

diff --git a/playbooks/roles/bootlinux/tasks/build/9p.yml b/playbooks/roles/bootlinux/tasks/build/9p.yml
index 1951e50e..98cbcb3c 100644
--- a/playbooks/roles/bootlinux/tasks/build/9p.yml
+++ b/playbooks/roles/bootlinux/tasks/build/9p.yml
@@ -44,6 +44,35 @@
     - bootlinux_tree_set_by_cli|bool
     - not target_directory_stat.stat.exists
 
+- name: Verify target git ref exists before cloning
+  command: "git ls-remote {{ target_linux_git }} {{ active_linux_ref | default(target_linux_ref) }}"
+  register: ref_check
+  run_once: true
+  delegate_to: localhost
+  when:
+    - not bootlinux_tree_set_by_cli|bool
+  tags: [ 'clone']
+
+- name: Fail if git ref does not exist
+  fail:
+    msg: |
+      Failed to verify git ref '{{ active_linux_ref | default(target_linux_ref) }}' exists in repository '{{ target_linux_git }}'.
+
+      This typically happens when:
+      1. The ref (branch/tag/commit) doesn't exist in the repository
+      2. You're using A/B testing with a shallow clone that doesn't contain the required ref
+      3. The repository URL is incorrect or inaccessible
+
+      Please verify:
+      - The ref '{{ active_linux_ref | default(target_linux_ref) }}' exists in the repository
+      - If using A/B testing with different refs, ensure shallow cloning is disabled
+      - The repository URL '{{ target_linux_git }}' is correct and accessible
+  when:
+    - not bootlinux_tree_set_by_cli|bool
+    - ref_check.rc != 0
+  run_once: true
+  delegate_to: localhost
+
 - name: git clone {{ target_linux_tree }} on the control node
   git:
     repo: "{{ target_linux_git }}"
diff --git a/playbooks/roles/bootlinux/tasks/build/builder.yml b/playbooks/roles/bootlinux/tasks/build/builder.yml
index c4c4b950..73cc6694 100644
--- a/playbooks/roles/bootlinux/tasks/build/builder.yml
+++ b/playbooks/roles/bootlinux/tasks/build/builder.yml
@@ -10,6 +10,27 @@
     - target_linux_install_b4
     - ansible_os_family == "Debian"
 
+- name: Verify target git ref exists before cloning
+  command: "git ls-remote {{ target_linux_git }} {{ target_linux_ref }}"
+  register: ref_check
+
+- name: Fail if git ref does not exist
+  fail:
+    msg: |
+      Failed to verify git ref '{{ target_linux_ref }}' exists in repository '{{ target_linux_git }}'.
+
+      This typically happens when:
+      1. The ref (branch/tag/commit) doesn't exist in the repository
+      2. You're using A/B testing with a shallow clone that doesn't contain the required ref
+      3. The repository URL is incorrect or inaccessible
+
+      Please verify:
+      - The ref '{{ target_linux_ref }}' exists in the repository
+      - If using A/B testing with different refs, ensure shallow cloning is disabled
+      - The repository URL '{{ target_linux_git }}' is correct and accessible
+  when:
+    - ref_check.rc != 0
+
 - name: Clone {{ target_linux_tree }}
   ansible.builtin.git:
     repo: "{{ target_linux_git }}"
diff --git a/playbooks/roles/bootlinux/tasks/build/targets.yml b/playbooks/roles/bootlinux/tasks/build/targets.yml
index 36339876..81465cc6 100644
--- a/playbooks/roles/bootlinux/tasks/build/targets.yml
+++ b/playbooks/roles/bootlinux/tasks/build/targets.yml
@@ -10,6 +10,28 @@
     - target_linux_install_b4
     - ansible_facts['os_family']|lower != 'debian'
 
+- name: Verify target git ref exists before cloning
+  command: "git ls-remote {{ target_linux_git }} {{ target_linux_ref }}"
+  register: ref_check
+  tags: [ 'clone']
+
+- name: Fail if git ref does not exist
+  fail:
+    msg: |
+      Failed to verify git ref '{{ target_linux_ref }}' exists in repository '{{ target_linux_git }}'.
+
+      This typically happens when:
+      1. The ref (branch/tag/commit) doesn't exist in the repository
+      2. You're using A/B testing with a shallow clone that doesn't contain the required ref
+      3. The repository URL is incorrect or inaccessible
+
+      Please verify:
+      - The ref '{{ target_linux_ref }}' exists in the repository
+      - If using A/B testing with different refs, ensure shallow cloning is disabled
+      - The repository URL '{{ target_linux_git }}' is correct and accessible
+  when:
+    - ref_check.rc != 0
+
 - name: git clone {{ target_linux_tree }} on the target nodes
   git:
     repo: "{{ target_linux_git }}"
-- 
2.47.2