pub global run should expose invocation metadata

[DartBot]

This issue was originally filed by @seaneagan

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If a script has a renamed executable like so:

executables:
  format: dartformat

Then it can be invoked in two different ways:

pub global run dart_style:format
dartformat

It would be useful if such apps can detect which way they were invoked to display appropriate help text, error messages, etc.

It could be exposed via either of:

* Platform.environment['PUB_GLOBAL_RUN_INVOCATION']

• const String.fromEnvironment('PUB_GLOBAL_RUN_INVOCATION')

The binstubs would set this before calling pub global run, and then `pub global run would initialize it using the invocation it received if it was not already set by the binstub.

So it's value would be e.g. "dartformat" or "pub global run dart_style:format"

[lrhn]

Added Area-Pub, Triaged labels.

[DartBot]

This comment was originally written by @seaneagan

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I just realized this is a similar request to issue #19580 that I previously posted.

However, the use case is different, and now that the pub [global] run stuff has settled down, I believe the problem and solution and pretty clear.

Also, it needs to handle pub run foo ... as well, so probably just PUB_RUN_INVOCATION, which in the case of pub run foo ... would be set to pub run foo

[DartBot]

This comment was originally written by @seaneagan

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Yet another use case:

seaneagan/unscripted#21 (comment)

[DartBot]

This issue has been moved to dart-lang/pub#1234.