feat(trycmd): Support echo text | command

[chrysn]

$ echo "hello" "second argument" | lines-from-stdin=1 bin-fixture
read line from stdin: hello second argument

Rather than attempting to do the common case and facing its security implications, this uses the fact that echo is defined in POSIX with a very small feature set, and that piping is a simple shell feature. The presence of the echo command is recognized (as any shell might recognize it) and evaluated into stdin data.

Closes: #172 (thus CC'ing @jpmckinney)

[edit: Add POSIX link]

[chrysn]

A test is included. In the project I'm using it in, switching from the published to the git version correctly shows that my README.md (which was ignored so far) is subtly lying, which is factually the correct result.

[epage]

Thank you for your interest in this! However, I feel it is premature to have a PR for this as we have not decided on a solution and solution discussions I feel are best left to issues. I have also found the existence of PRs are manipulative of maintainers, whether intended by the author or not, as maintainers want to honor the work that was done by people and work to merge it. Some maintainers recognize that and learn to not care at all. For myself, I've taken a fairly hard stance that I push back and close PRs.

[chrysn]

No pressure intended, happy to move the discussion back to #172. With the issue split out from #168, this sounded to me like the discussion was already complete by isolating the topic from command execution.