Revert "Remove tj-actions usage, eventhough we had it pinned as gitref"

[reakaleek]

Partially reverts #753 and updates to latest commit of tj-actions/changed-files

[Copilot]

Pull Request Overview

This PR reverts a previous commit that removed the usage of tj-actions and its pinning strategy, restoring the original flow for determining file changes and prompting additional execution conditions in the CI workflow. It also updates method signatures in RepositorySourcesFetcher.cs to include a new "name" parameter for improved logging in git command executions.

• Reintroduces the "Get changed files" step and adjusts conditional checks in the workflow.
• Modifies Exec and ExecIn method signatures to pass along a contextual parameter for logging.

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
.github/workflows/preview-build.yml	Restores tj-actions usage and updates conditions for checkout, deployment, documentation build, and link validation steps.
src/docs-assembler/Sourcing/RepositorySourcesFetcher.cs	Updates git command execution methods to include an additional parameter for improved logging context.

Comments suppressed due to low confidence (1)

src/docs-assembler/Sourcing/RepositorySourcesFetcher.cs:128

• [nitpick] Consider renaming the 'name' parameter to a more descriptive identifier (e.g., 'repoName') to clearly indicate its purpose in the context of git operations.

private void Exec(string name, string binary, params string[] args) => ExecIn(name, null, binary, args);