fast-export allows specifying revision ranges, which can be used to
export a tag without exporting the commit it tags. fast-export handled
this rather poorly: it would emit a "from :0" directive. Since marks
start at 1 and increase, this means it refers to an unknown commit and
fast-import will choke on the input.
When we are unable to look up a mark for the object being tagged, use a
"from $HASH" directive instead to fix this problem.
Note that this is quite similar to the behavior fast-export exhibits
with commits and parents when --reference-excluded-parents is passed
along with an excluded commit range. For tags of excluded commits we do
not require the --reference-excluded-parents flag because we always have
to tag something. By contrast, when dealing with commits, pruning a
parent is always a viable option, so we need the flag to specify that
parent pruning is not wanted. (It is slightly weird that
--reference-excluded-parents isn't the default with a separate
--prune-excluded-parents flag, but backward compatibility concerns
resulted in the current defaults.)
Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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