tests/csdiff: cover the line content matching by a test

... taken from a real-world example encountered
by differential-shellcheck:
redhat-plumbers-in-action/differential-shellcheck#376

Related: csutils#98
Closes: csutils#168

tests/csdiff/CMakeLists.txt

@@ -88,5 +88,6 @@ test_csdiff(diff-misc 20-shellcheck-line-content)
 test_csdiff(diff-misc 21-kernel-shell-code)
 test_csdiff(diff-misc 22-kernel-zstream-path)
 test_csdiff(diff-misc 23-cov-parser-key-event)
+test_csdiff(diff-misc 24-shellcheck-line-content)
 
 add_subdirectory(filter-file)

tests/csdiff/diff-misc/24-shellcheck-line-content-add-z.err

@@ -0,0 +1,23 @@
+Error: SHELLCHECK_WARNING:
+src/functions.sh:309:46: warning[SC2154]: GITHUB_REF is referenced but not assigned.
+#  307|     is_debug && local verbose=--verbose
+#  308|   
+#  309|->   echo '{"commit_oid":"'"${HEAD}"'","ref":"'"${GITHUB_REF//merge/head}"'","analysis_key":"differential-shellcheck","sarif":"'"$(gzip -c output.sarif | base64 -w0)"'","tool_names":["differential-shellcheck"]}' > payload.json
+#  310|   
+#  311|     local curl_args=(
+
+Error: SHELLCHECK_WARNING:
+src/functions.sh:309:129: info[SC2312]: Consider invoking this command separately to avoid masking its return value (or use '|| true' to ignore).
+#  307|     is_debug && local verbose=--verbose
+#  308|   
+#  309|->   echo '{"commit_oid":"'"${HEAD}"'","ref":"'"${GITHUB_REF//merge/head}"'","analysis_key":"differential-shellcheck","sarif":"'"$(gzip -c output.sarif | base64 -w0)"'","tool_names":["differential-shellcheck"]}' > payload.json
+#  310|   
+#  311|     local curl_args=(
+
+Error: SHELLCHECK_WARNING:
+src/functions.sh:309:152: info[SC2312]: Consider invoking this command separately to avoid masking its return value (or use '|| true' to ignore).
+#  307|     is_debug && local verbose=--verbose
+#  308|   
+#  309|->   echo '{"commit_oid":"'"${HEAD}"'","ref":"'"${GITHUB_REF//merge/head}"'","analysis_key":"differential-shellcheck","sarif":"'"$(gzip -c output.sarif | base64 -w0)"'","tool_names":["differential-shellcheck"]}' > payload.json
+#  310|   
+#  311|     local curl_args=(

tests/csdiff/diff-misc/24-shellcheck-line-content-add.err

@@ -0,0 +1,23 @@
+Error: SHELLCHECK_WARNING:
+src/functions.sh:309:46: warning[SC2154]: GITHUB_REF is referenced but not assigned.
+#  307|     is_debug && local verbose=--verbose
+#  308|   
+#  309|->   echo '{"commit_oid":"'"${HEAD}"'","ref":"'"${GITHUB_REF//merge/head}"'","analysis_key":"differential-shellcheck","sarif":"'"$(gzip -c output.sarif | base64 -w0)"'","tool_names":["differential-shellcheck"]}' > payload.json
+#  310|   
+#  311|     local curl_args=(
+
+Error: SHELLCHECK_WARNING:
+src/functions.sh:309:129: info[SC2312]: Consider invoking this command separately to avoid masking its return value (or use '|| true' to ignore).
+#  307|     is_debug && local verbose=--verbose
+#  308|   
+#  309|->   echo '{"commit_oid":"'"${HEAD}"'","ref":"'"${GITHUB_REF//merge/head}"'","analysis_key":"differential-shellcheck","sarif":"'"$(gzip -c output.sarif | base64 -w0)"'","tool_names":["differential-shellcheck"]}' > payload.json
+#  310|   
+#  311|     local curl_args=(
+
+Error: SHELLCHECK_WARNING:
+src/functions.sh:309:152: info[SC2312]: Consider invoking this command separately to avoid masking its return value (or use '|| true' to ignore).
+#  307|     is_debug && local verbose=--verbose
+#  308|   
+#  309|->   echo '{"commit_oid":"'"${HEAD}"'","ref":"'"${GITHUB_REF//merge/head}"'","analysis_key":"differential-shellcheck","sarif":"'"$(gzip -c output.sarif | base64 -w0)"'","tool_names":["differential-shellcheck"]}' > payload.json
+#  310|   
+#  311|     local curl_args=(