Have init script check for GitHub Actions

As well as still checking for Travis, for backward compatibility
and because experience shows that this is safe.

The check can be much broader, and would be more accurate, with
fewer false negatives. But a false positive can result in local
data loss because the script does hard resets on CI without
prompting for confirmation. So for now, this just checks $TRAVIS
and $GITHUB_ACTIONS.

Now that GHA is included, the CI workflows no longer need to set
$TRAVIS when running the script, so that is removed.

.github/workflows/cygwin-test.yml

@@ -40,7 +40,7 @@ jobs:
 
     - name: Prepare this repo for tests
       run: |
-        TRAVIS=yes ./init-tests-after-clone.sh
+        ./init-tests-after-clone.sh
 
     - name: Set git user identity and command aliases for the tests
       run: |

.github/workflows/pythonpackage.yml

@@ -37,7 +37,7 @@ jobs:
 
     - name: Prepare this repo for tests
       run: |
-        TRAVIS=yes ./init-tests-after-clone.sh
+        ./init-tests-after-clone.sh
 
     - name: Set git user identity and command aliases for the tests
       run: |

init-tests-after-clone.sh

@@ -2,7 +2,12 @@
 
 set -eu
 
-if test -z "${TRAVIS-}"; then
+ci() {
+    # For now, check just these, as a false positive could lead to data loss.
+    test -n "${TRAVIS-}" || test -n "${GITHUB_ACTIONS-}"
+}
+
+if ! ci; then
     printf 'This operation will destroy locally modified files. Continue ? [N/y]: ' >&2
     read -r answer
     case "$answer" in
@@ -29,7 +34,7 @@ git reset --hard HEAD~1
 git reset --hard __testing_point__
 
 # Do some setup that CI takes care of but that may not have been done locally.
-if test -z "${TRAVIS-}"; then
+if ! ci; then
     # The tests need some version tags. Try to get them even in forks.
     git fetch --all --tags