[llvm-cov] Create syntax to pass source w/o binary.

[mysterymath]

Summary

Since binary ID lookup makes CLI object arguments optional, it should be
possible to pass a list of source files without a binary. Unfortunately,
the current syntax will always interpret the first source file as a
binary. This change adds a -sources option to cause all later
positional arguments to be considered sources.

[mysterymath]

Correct .rst syntax.

[mysterymath]

Full diff.

[gulfem]

compiler-rt/test/profile/Linux/binary-id-lookup.c

14

Can you please extend this test to cover the following possible combinations in llvm-cov as well?

1. object file(s) and source file(s)
2. debug-file-directory, object file(s) and source file(s)

[gulfem]

Please remove the dot at the end of the commit message.

[mysterymath]

Address review feedback.

compiler-rt/test/profile/Linux/binary-id-lookup.c

 // REQUIRES: linux
 // RUN: split-file %s %t
 // RUN: %clang_profgen -Wl,--build-id=0x12345678 -fcoverage-mapping -O2 -shared %t/foo.c -o %t/libfoo.so
 // RUN: %clang_profgen -Wl,--build-id=0xabcd1234 -fcoverage-mapping -O2 %t/main.c -L%t -lfoo -o %t.main
 // RUN: rm -rf %t.profdir
 // RUN: env LLVM_PROFILE_FILE=%t.profdir/default_%m.profraw LD_LIBRARY_PATH=%t %run %t.main
 // RUN: mkdir -p %t/.build-id/12 %t/.build-id/ab
 // RUN: cp %t/libfoo.so %t/.build-id/12/345678.debug
 // RUN: cp %t.main %t/.build-id/ab/cd1234.debug
 // RUN: llvm-profdata merge -o %t.profdata %t.profdir/default_*.profraw
 // RUN: llvm-cov show -instr-profile %t.profdata -debug-file-directory %t | FileCheck %s
+// RUN: llvm-cov show -instr-profile %t.profdata -debug-file-directory %t -sources %t/foo.c | FileCheck %s --check-prefix=FOO-ONLY
 // RUN: echo "bad" > %t/.build-id/ab/cd1234.debug
 // RUN: llvm-cov show -instr-profile %t.profdata -debug-file-directory %t %t.main | FileCheck %s
 // RUN: not llvm-cov show -instr-profile %t.profdata -debug-file-directory %t/empty 2>&1 | FileCheck %s --check-prefix=NODATA
 
 // CHECK: 1| 1|void foo(void) {}
 // CHECK: 2| 1|void bar(void) {}
 // CHECK: 3| 1|int main() {
 
+// FOO-ONLY: 1| 1|void foo(void) {}
 // NODATA: error: Failed to load coverage: '': No coverage data found
 
 //--- foo.c
 void foo(void) {}
 
 //--- main.c
 void foo(void);
 void bar(void) {}
 int main() {
   foo();
   bar();
   return 0;
 }

llvm/docs/CommandGuide/llvm-cov.rst

 .. _llvm-cov-show:
 
 SHOW COMMAND
 ------------
 
 SYNOPSIS
 ^^^^^^^^
 
-:program:`llvm-cov show` [*options*] -instr-profile *PROFILE* *BIN* [*-object BIN,...*] [[*-object BIN*]] [*SOURCES*]
+:program:`llvm-cov show` [*options*] -instr-profile *PROFILE* [*BIN*] [*-object BIN*]... [*-sources*] [*SOURCE*]...
 
 DESCRIPTION
 ^^^^^^^^^^^
 
 The :program:`llvm-cov show` command shows line by line coverage of the
 binaries *BIN*,...  using the profile data *PROFILE*. It can optionally be
 filtered to only show the coverage for the files listed in *SOURCES*.
 

 .. _llvm-cov-report:
 
 REPORT COMMAND
 --------------
 
 SYNOPSIS
 ^^^^^^^^
 
-:program:`llvm-cov report` [*options*] -instr-profile *PROFILE* *BIN* [*-object BIN,...*] [[*-object BIN*]] [*SOURCES*]
+:program:`llvm-cov report` [*options*] -instr-profile *PROFILE* [*BIN*] [*-object BIN*]... [*-sources*] [*SOURCE*]...
 
 DESCRIPTION
 ^^^^^^^^^^^
 
 The :program:`llvm-cov report` command displays a summary of the coverage of
 the binaries *BIN*,... using the profile data *PROFILE*. It can optionally be
 filtered to only show the coverage for the files listed in *SOURCES*.
 

 .. _llvm-cov-export:
 
 EXPORT COMMAND
 --------------
 
 SYNOPSIS
 ^^^^^^^^
 
-:program:`llvm-cov export` [*options*] -instr-profile *PROFILE* *BIN* [*-object BIN,...*] [[*-object BIN*]] [*SOURCES*]
+:program:`llvm-cov export` [*options*] -instr-profile *PROFILE* [*BIN*] [*-object BIN*]... [*-sources*] [*SOURCE*]...
 
 DESCRIPTION
 ^^^^^^^^^^^
 
 The :program:`llvm-cov export` command exports coverage data of the binaries
 *BIN*,... using the profile data *PROFILE* in either JSON or lcov trace file
 format.
 

llvm/tools/llvm-cov/CodeCoverage.cpp

int CodeCoverageTool::run(Command Cmd, int argc, const char **argv) {
 
   cl::list<std::string> CovFilenames(
       "object", cl::desc("Coverage executable or object file"));
 
   cl::opt<bool> DebugDumpCollectedObjects(
       "dump-collected-objects", cl::Optional, cl::Hidden,
       cl::desc("Show the collected coverage object files"));
 
-  cl::list<std::string> InputSourceFiles(cl::Positional,
+  cl::list<std::string> InputSourceFiles("sources", cl::Positional,
                                          cl::desc("<Source files>"));
 
   cl::opt<bool> DebugDumpCollectedPaths(
       "dump-collected-paths", cl::Optional, cl::Hidden,
       cl::desc("Show the collected paths to source files"));
 
   cl::opt<std::string, true> PGOFilename(
       "instr-profile", cl::Required, cl::location(this->PGOFilename),