Remove dap_full_clone feature flag

What does this MR do and why?

Removes the dap_full_clone feature flag now that it has been rolled out to 100% and is default-on.

The flag controlled whether Duo Workflow workloads use a full blobless clone (GIT_DEPTH=0) instead of a shallow clone. Since it is now always enabled, the flag check is removed and the full-clone behavior is inlined unconditionally in StartWorkflowService.

Changes:

• Delete ee/config/feature_flags/development/dap_full_clone.yml
• Remove full_clone? and inline the always-true behavior in git_clone_variables and workspace_fixup_commands
• Remove the legacy shallow-clone path, which was only reachable when dap_full_clone was disabled
• Drop spec coverage for the disabled path; keep and simplify the enabled-path specs

Why a second feature flag is removed here

This MR also deletes ee/config/feature_flags/gitlab_com_derisk/dap_git_tree_zero_option.yml, which is owned by group::agent foundations.

Removing dap_full_clone made the legacy shallow-clone branch unreachable, and that branch held the only code reference to dap_git_tree_zero_option. An orphaned flag definition fails the rspec:feature-flags job, so the definition has to go in the same MR:

These feature flags appear to be UNUSED
- dap_git_tree_zero_option
Feature flag usage check failed.

The --filter=tree:0 option was never rolled out. Its rollout issue has none of its 38 steps completed, it is a gitlab_com_derisk flag well past that type's documented two-month lifespan (introduced in 18.11), and the code path it guarded has been unreachable on GitLab.com since dap_full_clone reached 100%. So nothing live is lost.

/cc @igor.drozdov — flagging since dap_git_tree_zero_option is yours. If the tree:0 experiment is still wanted, it needs rebuilding on top of the full clone rather than kept alive here.

Update: I aligned with Igor that we can savely remove dap_git_tree_zero_option

Remaining manual steps after deploy

• /chatops gitlab run feature delete dap_full_clone --dev --pre --staging --staging-ref --production
• /chatops gitlab run feature delete dap_git_tree_zero_option --dev --pre --staging --staging-ref --production
• Close [FF] `dap_full_clone` -- Roll out full-clone wo... (#602990 - closed)
• Close [FF] `dap_git_tree_zero_option` -- Rollout or -... (#595729 - closed)

Related MR

The now-ignored shallow_clone API parameter is removed separately in !250447 (merged).

References

• Rollout issue: #602990 (closed)
• dap_git_tree_zero_option rollout issue: #595729 (closed)
• Follow-up MR: !250447 (merged)

How to set up and validate locally

• Checkout this branch and restart your gdk

• Trigger a duo developer flow or another foundational- or custom flow

• The flow should execute without any issues (and you should see the full clone happening in the job logs)

  

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