[Merge] ~racb/ubuntu-dev-tools:diff-gz-identity into ubuntu-dev-tools:main

[Sebastien Bacher]

Review: Approve

Thanks, the explanations on the bug are convincing to me and the code changes match what was described (+bonus points for documenting the reason)
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https://code.launchpad.net/~racb/ubuntu-dev-tools/+git/ubuntu-dev-tools/+merge/446078
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