I've spent a good time trying to figure out what the issue could be, but I couldn't.
$ FILES=$(git diff --name-only --diff-filter=ACMR HEAD origin/${CI_MERGE_REQUEST_TARGET_BRANCH_NAME} -- '*.php' '*.inc')
$ FILES=${FILES//$'\n'/ }
$ [[ -z "$FILES" ]] && { echo "Nothing to check": exit 0; }
$ echo "Checking ${FILES}"
Checking sitepress.php
$ echo "${FILES}" > ./files.txt
$ cat ./files.txt
sitepress.php
$ echo "Running checks..."
Running checks...
$ ./vendor/bin/phpcs --standard=./phpcs.xml --report=json --file-list=./files.txt || true > ./phpcs.json
{"totals":{"errors":39,"warnings":7,"fixable":12},"files":{"\/builds\/wpml\/sitepress-multilingual-cms\/sitepress.php":{"errors":39,"warnings":7,"messages":[{"message":"You must use \"\/**\" style comments for a file comment","source":"Squiz.Commenting.FileComment.WrongStyle","severity":5,"fixable":false,"type":"ERROR","line":2,"column":1},{"message":"Empty line required before block comment","source":"Squiz.Commenting.BlockComment.NoEmptyLineBefore","severity":5,"fixable":false,"type":"ERROR","line":2,"column":1},{"message":"No space found before comment text; expected \"\/\/ define('ICL_SITEPRESS_DEV_VERSION', '3.4-dev');\" but found \"\/\/define('ICL_SITEPRESS_DEV_VERSION', '3.4-dev');\"","source":"Squiz.Commenting.InlineComment.NoSpaceBefore","severity":5,"fixable":true,"type":"ERROR","line":25,"column":1},{"message":"Inline comments must end in full-stops, exclamation marks, or question marks","source":"Squiz.Commenting.InlineComment.InvalidEndChar","severity":5,"fixable":false,"type":"ERROR","line":25,"column":1},{"message":"Missing short description in doc comment","source":"Generic.Commenting.DocComment.MissingShort","severity":5,"fixable":false,"type":"ERROR","line":31,"column":1},{"message":"Missing short description in doc comment","source":"Generic.Commenting.DocComment.MissingShort","severity":5,"fixable":false,"type":"ERROR","line":33,"column":1},{"message":"Missing short description in doc comment","source":"Generic.Commenting.DocComment.MissingShort","severity":5,"fixable":false,"type":"ERROR","line":35,"column":1},{"message":"Missing short description in doc comment","source":"Generic.Commenting.DocComment.MissingShort","severity":5,"fixable":false,"type":"ERROR","line":37,"column":1},{"message":"No space found before comment text; expected \"\/\/ PHP 5.2 backward compatibility\" but found \"\/\/PHP 5.2 backward compatibility\"","source":"Squiz.Commenting.InlineComment.NoSpaceBefore","severity":5,"fixable":true,"type":"ERROR","line":40,"column":1},{"message":"Inline comments must end in full-stops, exclamation marks, or question marks","source":"Squiz.Commenting.InlineComment.InvalidEndChar","severity":5,"fixable":false,"type":"ERROR","line":40,"column":1},{"message":"Variable \"WPML_Dependencies\" is not in valid snake_case format","source":"WordPress.NamingConventions.ValidVariableName.NotSnakeCase","severity":5,"fixable":false,"type":"ERROR","line":54,"column":1},{"message":"\"require_once\" is a statement not a function; no parentheses are required","source":"PEAR.Files.IncludingFile.BracketsNotRequired","severity":5,"fixable":true,"type":"WARNING","line":97,"column":1},{"message":"Inline comments must end in full-stops, exclamation marks, or question marks","source":"Squiz.Commenting.InlineComment.InvalidEndChar","severity":5,"fixable":false,"type":"ERROR","line":120,"column":1},{"message":"No space found before comment text; expected \"\/\/ Set cron job to update WPML config index file from CDN\" but found \"\/\/Set cron job to update WPML config index file from CDN\"","source":"Squiz.Commenting.InlineComment.NoSpaceBefore","severity":5,"fixable":true,"type":"ERROR","line":147,"column":5},{"message":"Inline comments must end in full-stops, exclamation marks, or question marks","source":"Squiz.Commenting.InlineComment.InvalidEndChar","severity":5,"fixable":false,"type":"ERROR","line":147,"column":5},{"message":"Missing short description in doc comment","source":"Generic.Commenting.DocComment.MissingShort","severity":5,"fixable":false,"type":"ERROR","line":150,"column":1},{"message":"Missing short description in doc comment","source":"Generic.Commenting.DocComment.MissingShort","severity":5,"fixable":false,"type":"ERROR","line":151,"column":1},{"message":"Missing short description in doc comment","source":"Generic.Commenting.DocComment.MissingShort","severity":5,"fixable":false,"type":"ERROR","line":239,"column":1},{"message":"Missing short description in doc comment","source":"Generic.Commenting.DocComment.MissingShort","severity":5,"fixable":false,"type":"ERROR","line":246,"column":1},{"message":"Missing short description in doc comment","source":"Generic.Commenting.DocComment.MissingShort","severity":5,"fixable":false,"type":"ERROR","line":268,"column":5},{"message":"Found precision alignment of 3 spaces.","source":"WordPress.WhiteSpace.PrecisionAlignment.Found","severity":5,"fixable":false,"type":"WARNING","line":275,"column":1},{"message":"Tabs must be used to indent lines; spaces are not allowed","source":"Generic.WhiteSpace.DisallowSpaceIndent.SpacesUsed","severity":5,"fixable":true,"type":"ERROR","line":275,"column":1},{"message":"Inline comments must end in full-stops, exclamation marks, or question marks","source":"Squiz.Commenting.InlineComment.InvalidEndChar","severity":5,"fixable":false,"type":"ERROR","line":279,"column":1},{"message":"Variable \"WPML_Users_Languages_Dependencies\" is not in valid snake_case format","source":"WordPress.NamingConventions.ValidVariableName.NotSnakeCase","severity":5,"fixable":false,"type":"ERROR","line":284,"column":1},{"message":"Missing doc comment for function wpml_init_language_switcher()","source":"Squiz.Commenting.FunctionComment.Missing","severity":5,"fixable":false,"type":"ERROR","line":286,"column":1},{"message":"Missing doc comment for function wpml_mlo_init()","source":"Squiz.Commenting.FunctionComment.Missing","severity":5,"fixable":false,"type":"ERROR","line":293,"column":1},{"message":"Missing short description in doc comment","source":"Generic.Commenting.DocComment.MissingShort","severity":5,"fixable":false,"type":"ERROR","line":301,"column":1},{"message":"Missing parameter comment","source":"Squiz.Commenting.FunctionComment.MissingParamComment","severity":5,"fixable":false,"type":"ERROR","line":302,"column":4},{"message":"There must be exactly one blank line before the tags in a doc comment","source":"Generic.Commenting.DocComment.SpacingBeforeTags","severity":5,"fixable":true,"type":"ERROR","line":311,"column":8},{"message":"Found precision alignment of 1 spaces.","source":"WordPress.WhiteSpace.PrecisionAlignment.Found","severity":5,"fixable":false,"type":"WARNING","line":314,"column":1},{"message":"Tabs must be used to indent lines; spaces are not allowed","source":"Generic.WhiteSpace.DisallowSpaceIndent.SpacesUsed","severity":5,"fixable":true,"type":"ERROR","line":314,"column":1},{"message":"Found precision alignment of 1 spaces.","source":"WordPress.WhiteSpace.PrecisionAlignment.Found","severity":5,"fixable":false,"type":"WARNING","line":315,"column":1},{"message":"Tabs must be used to indent lines; spaces are not allowed","source":"Generic.WhiteSpace.DisallowSpaceIndent.SpacesUsed","severity":5,"fixable":true,"type":"ERROR","line":315,"column":1},{"message":"No space before closing parenthesis is prohibited","source":"WordPress.WhiteSpace.ControlStructureSpacing.NoSpaceBeforeCloseParenthesis","severity":5,"fixable":true,"type":"ERROR","line":315,"column":67},{"message":"Missing doc comment for function wpml_integrations_requirements()","source":"Squiz.Commenting.FunctionComment.Missing","severity":5,"fixable":false,"type":"ERROR","line":334,"column":1},{"message":"Missing doc comment for function wpml_troubleshoot_action_load()","source":"Squiz.Commenting.FunctionComment.Missing","severity":5,"fixable":false,"type":"ERROR","line":341,"column":1},{"message":"Missing doc comment for function wpml_init_language_cookie_settings()","source":"Squiz.Commenting.FunctionComment.Missing","severity":5,"fixable":false,"type":"ERROR","line":352,"column":1},{"message":"Found precision alignment of 1 spaces.","source":"WordPress.WhiteSpace.PrecisionAlignment.Found","severity":5,"fixable":false,"type":"WARNING","line":358,"column":1},{"message":"Tabs must be used to indent lines; spaces are not allowed","source":"Generic.WhiteSpace.DisallowSpaceIndent.SpacesUsed","severity":5,"fixable":true,"type":"ERROR","line":358,"column":1},{"message":"Found precision alignment of 2 spaces.","source":"WordPress.WhiteSpace.PrecisionAlignment.Found","severity":5,"fixable":false,"type":"WARNING","line":359,"column":1},{"message":"Tabs must be used to indent lines; spaces are not allowed","source":"Generic.WhiteSpace.DisallowSpaceIndent.SpacesUsed","severity":5,"fixable":true,"type":"ERROR","line":359,"column":1},{"message":"Missing doc comment for function wpml_check_php_version()","source":"Squiz.Commenting.FunctionComment.Missing","severity":5,"fixable":false,"type":"ERROR","line":377,"column":1},{"message":"Comma not allowed after last value in single-line array declaration","source":"WordPress.Arrays.CommaAfterArrayItem.CommaAfterLast","severity":5,"fixable":true,"type":"ERROR","line":383,"column":52},{"message":"Missing doc comment for function wpml_core_loads_first()","source":"Squiz.Commenting.FunctionComment.Missing","severity":5,"fixable":false,"type":"ERROR","line":389,"column":1},{"message":"Variable assignment found within a condition. Did you mean to do a comparison?","source":"WordPress.CodeAnalysis.AssignmentInCondition.Found","severity":5,"fixable":false,"type":"WARNING","line":392,"column":27},{"message":"Assignments must be the first block of code on a line","source":"Squiz.PHP.DisallowMultipleAssignments.Found","severity":5,"fixable":false,"type":"ERROR","line":392,"column":27}]}}}$ cat ./phpcs.json
$ echo "Parsing results..."
Parsing results...
$ ./vendor/bin/diffFilter --phpcs files.txt ./phpcs.json 100
Can't Parse phpcs json - Syntax error
Job succeeded
I hope this is enough data to help me figure out what's wrong here.