view CONTRIBUTING @ 41218:24a1f67bb75a

revset: enforce "%d" to be interpreted as literal revision number (API) (BC)

Before this change, `formatspec("%d", x)` results in `"%d" % int(x)`. This
seems simple and correct until you consider `nullrev`. In revset, a direct
"-1" symbol is equivalent to `tip` not `nullrev`. This is a subtle error that
went undetected for a while. Wrapping the revision number inside 'rev()'
remove the ambiguity, preserving nullrev value passed to formatspec.

It got caught by the rebase code, were the following wrongly returned `[1]`:

    repo.revs("children(%d) and ancestors(%ld)", 0, [nullrev])

This is flagged as API, because `%d` can be used for non-revision integer
argument of revset function. We probably need to introduce a new '%…'
substitution to allow literal integer (maybe `%i`). However, the `%d` usage is
currently widespread for revision number so it is important to fix this issue
for `%d`.  This choice is reinforced by the fact _intlist is implemented as
revisions only. Restricting `%d` to revision only makes things more
consistent.

This bug can become especially tricky since `_intlist` recognize `nullrev`
right. So `revs('%ld', [-1, 0])` → select `[nullrev, 0]` but `revs('%ld',
[-1])` is simplified and treated as `%d` selecting `[tip]`.

Another side effect is that "%d" of an unknown revision simply match nothing. It
was previously raising and error. This is consistent with what "%ld" (and
`_intlist`) is doing, so it seems like a good move.

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