shellCommand

Split out from #33 because it is a bit more complicated.

ShellCommandRequirement

Becomes "shellCommand" on CommandLineTool with value 'true' or 'false' (default is 'false') but with different semantics than "ShellCommandRequirement".

Having "shellCommand: true" (or "useShell: true" or whatever we call it) specifies semantics so that

• it is run with /bin/sh -c
• the command line is constructed such that each component is added to the command line separated by spaces and but any parameter substitutions are quoted. Quoting parameter substitutions can be suppressed using 'shellQuote: false', but I think in most cases this won't be necessary (and presents the opportunity for shell injection, so it should be strongly discouraged).

This differs from ShellCommandRequirement where each element of the command line is quoted by default unless 'shellQuote: false' is present, which makes it very awkward to use shell metacharacters even when it is safe to do so.

No files or tests are named. Start by locating the CommandLineTool and ShellCommandRequirement definitions, then compare their documented semantics; done means the proposed shellCommand behavior, defaults, quoting rules, and /bin/sh -c execution are specified and covered by the project’s relevant validation.