[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

 // 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: 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

llvm/docs/CommandGuide/llvm-cov.rst

 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*.
+binaries *BIN*...  using the profile data *PROFILE*. It can optionally be
+filtered to only show the coverage for the files listed in *SOURCE*....
 
 *BIN* may be an executable, object file, dynamic library, or archive (thin or
 otherwise).

 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*.
+the binaries *BIN*... using the profile data *PROFILE*. It can optionally be
+filtered to only show the coverage for the files listed in *SOURCE*....
 
 *BIN* may be an executable, object file, dynamic library, or archive (thin or
 otherwise).

 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
+*BIN*... using the profile data *PROFILE* in either JSON or lcov trace file
 format.
 
 When exporting JSON, the regions, functions, branches, expansions, and

 file, the line-based coverage, branch coverage, and summaries will be exported.
 
 The exported data can optionally be filtered to only export the coverage
-for the files listed in *SOURCES*.
+for the files listed in *SOURCE*....
 
 For information on compiling programs for coverage and generating profile data,
 see :ref:`llvm-cov-show`.

llvm/tools/llvm-cov/CodeCoverage.cpp

       "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(