enhance: Add comprehensive .gitignore for deb-mock project

- Add mock-specific build artifacts (chroot/, mock-*, mockroot/)
- Include package build files (*.deb, *.changes, *.buildinfo)
- Add development tools (.coverage, .pytest_cache, .tox)
- Include system files (.DS_Store, Thumbs.db, ._*)
- Add temporary and backup files (*.tmp, *.bak, *.backup)
- Include local configuration overrides (config.local.yaml, .env.local)
- Add test artifacts and documentation builds
- Comprehensive coverage for Python build system project

This ensures build artifacts, chroot environments, and development
tools are properly ignored in version control.

testing-farm/tests/behave/main.fmf

@@ -0,0 +1,9 @@
+---
+summary: Execute the behave test
+test: ./test.sh
+tag: behave
+duration: 2h
+
+require:
+  - type: file
+    pattern: /behave

testing-farm/tests/behave/test.sh

@@ -0,0 +1,5 @@
+#!/bin/sh -eux
+
+cd ../../../behave
+install-mock-packages-built-by-packit mock-core-configs mock
+behave

testing-farm/tests/old-testsuite/main.fmf

@@ -0,0 +1,11 @@
+---
+summary: Execute the old `make check` test-suite
+test: ./test.sh
+tag: old_testsuite
+duration: 3h
+tty: true
+
+require:
+  - type: file
+    # copy-paste the whole directory
+    pattern: /

testing-farm/tests/old-testsuite/test.sh

@@ -0,0 +1,28 @@
+#!/bin/bash -eux
+
+# The Mock's test-suite is designed for the mockbuild users.  Copy files to a
+# separate directory where the 'mockbuild' user has a full access.
+workdir=$(mktemp -d --suffix=-mock-old-tests)
+rsync -ra ../../../ "$workdir"
+chown -R mockbuild:mockbuild "$workdir"
+
+# TODO: Mock should work with 'rw-------' files too.
+# https://github.com/rpm-software-management/mock/issues/1300
+chmod a+r "$workdir/mock/integration-tests"/test-*
+
+# Install the tested RPMs
+install-mock-packages-built-by-packit mock-core-configs mock
+
+# Download the tested SRPM
+SRPM_DOWNLOAD_DIR=/tmp/mock-test-srpms install-mock-packages-built-by-packit mock
+
+cd "$workdir/mock"
+
+# We want to provide rather short live logs ASAP, hence that grep.  Full logs
+# are provided later no matter the exit status.
+exit_status=0
+sudo -E -u mockbuild make check |& tee the-log | grep -e FAILED: -e PASSED: || {
+    exit_status=$?
+}
+cat the-log
+exit $exit_status