[LTR] Infer kernel version from UPSTREAM_REF

[bmastbergen]

Use the inferred kernel version to construct all of the other branch references in the script. This should allow an UPSTREAM_REF of stable_6.18.y to be passed and the script to work the same way it does today for 6.12

[Copilot]

Pull request overview

This PR refactors the lt_rebase.sh script to dynamically infer the kernel version from the UPSTREAM_REF parameter instead of hardcoding version "6.12". This enables the script to work seamlessly with different kernel versions (e.g., stable_6.18.y) by extracting the version number and constructing all branch references dynamically.

Key changes:

• Added kernel version extraction logic using regex pattern matching on UPSTREAM_REF
• Replaced all hardcoded "6.12" references with the dynamically extracted KERNEL_VERSION variable
• Added validation and error handling for version extraction with clear error messages

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[Copilot]

Pull request overview

Copilot reviewed 1 out of 1 changed files in this pull request and generated 2 comments.

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[Copilot]

The validation pattern stable_[0-9]*.[0-9]*.y uses glob patterns which are more permissive than intended. This would accept invalid formats like stable_123.y (missing second version number) or stable_.1.y (missing first version number). Consider using a more restrictive pattern like stable_[0-9]*[0-9].[0-9]*[0-9].y or handle validation in the extraction step.

[PlaidCat]

I can't see a condition where the upstream forgets to label this correctly.

[bmastbergen]

UPSTREAM_REF is optionally assigned by command line argument here, so this is just some validation that it is a reasonable value.

[roxanan1996]

I would replace '*" with '+' to be the same as the regex below.

[bmastbergen]

yea, good call. I made the regexs the same. Thanks!