Fix unit tests to pass for newer OpenSSL versions

Adjust a couple of output checks to look for expected text anywhere
in the output, instead of at specific lines, so tests will pass
despite warning output like this:

    *** WARNING : deprecated key derivation used.
    Using -iter or -pbkdf2 would be better.

See also #55

.github/workflows/run-bats-core-tests.yml

@@ -10,9 +10,8 @@ on:
 
 jobs:
   test:
-    # We use older Ubuntu for now to avoid warning from newer OpenSSL (#55)
-    # which break output expectations in some (fragile) tests
-    runs-on: ubuntu-16.04
+    # Test on older Ubuntu with OpenSSL < 1.1 and newer with OpenSSL >= 1.1
+    runs-on: [ubuntu-16.04, ubuntu-18.04]
 
     steps:
     # Checks-out your repository under $GITHUB_WORKSPACE, so your job can access it

tests/test_merge.bats

@@ -86,7 +86,7 @@ load $BATS_TEST_DIRNAME/_test_helper.bash
 
   run git merge branch-2
   [ "$status" -ne 0 ]
-  [ "${lines[1]}" = "CONFLICT (content): Merge conflict in sensitive_file" ]
+  [[ "${output}" = *"CONFLICT (content): Merge conflict in sensitive_file"* ]]
 
   run cat sensitive_file
   [ "$status" -eq 0 ]

tests/test_pre_commit.bats

@@ -44,11 +44,11 @@ load $BATS_TEST_DIRNAME/_test_helper.bash
   # an encrypted file
   run git commit -m "Added more"
   [ "$status" -ne 0 ]
-  [ "${lines[0]}" = "Transcrypt managed file is not encrypted in the Git index: sensitive_file" ]
-  [ "${lines[1]}" = "You probably staged this file using a tool that does not apply .gitattribute filters as required by Transcrypt." ]
-  [ "${lines[2]}" = "Fix this by re-staging the file with a compatible tool or with Git on the command line:" ]
-  [ "${lines[3]}" = "    git reset -- sensitive_file" ]
-  [ "${lines[4]}" = "    git add sensitive_file" ]
+  [[ "${output}" = *"Transcrypt managed file is not encrypted in the Git index: sensitive_file"* ]]
+  [[ "${output}" = *"You probably staged this file using a tool that does not apply .gitattribute filters as required by Transcrypt."* ]]
+  [[ "${output}" = *"Fix this by re-staging the file with a compatible tool or with Git on the command line:"* ]]
+  [[ "${output}" = *"    git reset -- sensitive_file"* ]]
+  [[ "${output}" = *"    git add sensitive_file"* ]]
 }
 
 @test "pre-commit: warn and don't clobber existing pre-commit hook on init" {