[FileCheck] Parse command-line options from FILECHECK_OPTS

This feature makes it easy to tune FileCheck diagnostic output when
running the test suite via ninja, a bot, or an IDE.  For example:

```
$ FILECHECK_OPTS='-color -v -dump-input-on-failure' \
  LIT_FILTER='OpenMP/for_codegen.cpp' ninja check-clang \
  | less -R
```

Reviewed By: probinson

Differential Revision: https://reviews.llvm.org/D53517

llvm-svn: 346272

1 files changed, 10 insertions, 1 deletions

diff --git a/llvm/include/llvm/Support/CommandLine.h b/llvm/include/llvm/Support/CommandLine.h
index 799b41fbf8b..cd3543c130e 100644
--- a/llvm/include/llvm/Support/CommandLine.h
+++ b/llvm/include/llvm/Support/CommandLine.h
@@ -56,9 +56,18 @@ namespace cl {
 // Returns true on success. Otherwise, this will print the error message to
 // stderr and exit if \p Errs is not set (nullptr by default), or print the
 // error message to \p Errs and return false if \p Errs is provided.
+//
+// If EnvVar is not nullptr, command-line options are also parsed from the
+// environment variable named by EnvVar.  Precedence is given to occurrences
+// from argv.  This precedence is currently implemented by parsing argv after
+// the environment variable, so it is only implemented correctly for options
+// that give precedence to later occurrences.  If your program supports options
+// that give precedence to earlier occurrences, you will need to extend this
+// function to support it correctly.
 bool ParseCommandLineOptions(int argc, const char *const *argv,
                              StringRef Overview = "",
-                             raw_ostream *Errs = nullptr);
+                             raw_ostream *Errs = nullptr,
+                             const char *EnvVar = nullptr);
 
 //===----------------------------------------------------------------------===//
 // ParseEnvironmentOptions - Environment variable option processing alternate