Due to the lazy initialization of lines in the Alacritty history, the
recording of ref tests was broken. Because a WM would often resize the
ref test window after it was spawned, some additional lines were
initialized in the stored ref test.
To make sure lazy initialization does not play any role in the recording
and replaying of reftests, before recording and replaying the tests, the
complete grid is initialized and then truncated. This should make sure
that only the relevant lines are kept.
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