Fix /review trigger when comment has leading whitespace

[JanKrivanek]

Note

Are you waiting for the changes in this PR to be merged?
It would be very helpful if you could test the resulting artifacts from this PR and let us know in a comment if this change resolves your issue. Thank you!

Problem

The /review slash command in .github/workflows/review-trigger.yml is silently skipped when the comment body has any leading whitespace before /review.

Concrete example:

• Comment posted on Fix intermediate pages not receiving query parameters in multi-page Shell navigation #35432: Fix intermediate pages not receiving query parameters in multi-page Shell navigation #35432 (comment)
• Body (raw bytes): ' /review -b feature/regression-check' — note the leading space (0x20).
• Result: workflow run https://github.com/dotnet/maui/actions/runs/25824871590 → skipped.

Root cause

The job-level guard was:

if: >-
  github.event_name == 'workflow_dispatch' ||
  (github.event.issue.pull_request &&
   (github.event.comment.body == '/review' ||
    startsWith(github.event.comment.body, '/review ')))

startsWith(' /review ...', '/review ') returns false, so the job is skipped. GitHub expression syntax has no trim or regex, so we can't fix this purely at the expression level. The Parse parameters step had the same blind spot — sed -n 's|^/review[[:space:]]*||p' produces empty ARGS if the body doesn't start with /review.

Fix

1. New tiny match pre-filter job that uses a bash regex (^[[:space:]]*/review([[:space:]]|$)) to decide whether the comment is a /review command. It allows arbitrary leading whitespace (spaces, tabs, newlines) but still requires /review to be a standalone token (won't match /reviewfoo or comments that merely mention /review mid-sentence).
2. trigger-review now needs: match and gates on its output, keeping the rest of the job structure intact.
3. Trim leading whitespace before sed in Parse parameters, so flag/positional parsing works on prefixed comments like /review -b feature/foo.

Verification

Local check of the regex against representative inputs:

Body	Should match	Matches
/review	yes	yes
/review android	yes	yes
/review -b feature/regression-check (the failing case)	yes	yes
\t/review	yes	yes
/review -p ios	yes	yes
/reviewfoo	no	no
please /review this	no	no
not a command	no	no

The full end-to-end behavior will be exercised by the next /review invocation on a PR that targets this branch.

[github-actions]

🚀 Dogfood this PR with:

⚠️ WARNING: Do not do this without first carefully reviewing the code of this PR to satisfy yourself it is safe.

curl -fsSL https://raw.githubusercontent.com/dotnet/maui/main/eng/scripts/get-maui-pr.sh | bash -s -- 35438

Or

• Run remotely in PowerShell:

iex "& { $(irm https://raw.githubusercontent.com/dotnet/maui/main/eng/scripts/get-maui-pr.ps1) } 35438"

[JanKrivanek]

/azp run maui-pr-uitests, maui-pr-devicetests

[azure-pipelines]

Azure Pipelines could not run because the pipeline triggers exclude this branch/path.