view mercurial/help/multirevs.txt @ 26402:05871262acd5

treemanifest: rework lazy-copying code (issue4840)

The old lazy-copy code formed a chain of copied manifests with each
copy. Under typical operation, the stack never got more than a couple
of manifests deep and was fine. Under conditions like hgsubversion or
convert, the stack could get hundreds of manifests deep, and
eventually overflow the recursion limit for Python. I was able to
consistently reproduce this by converting an hgsubversion clone of
svn's history to treemanifests.

This may result in fewer manifests staying in memory during operations
like convert when treemanifests are in use, and should make those
operations faster since there will be significantly fewer noop
function calls going on.

A previous attempt (never mailed) of mine to fix this problem tried to
simply have all treemanifests only have a loadfunc - that caused
somewhat weird problems because the gettext() callable passed into
read() wasn't idempotent, so the easy solution is to have a loadfunc
and a copyfunc.

When Mercurial accepts more than one revision, they may be specified
individually, or provided as a topologically continuous range,
separated by the ":" character.

The syntax of range notation is [BEGIN]:[END], where BEGIN and END are
revision identifiers. Both BEGIN and END are optional. If BEGIN is not
specified, it defaults to revision number 0. If END is not specified,
it defaults to the tip. The range ":" thus means "all revisions".

If BEGIN is greater than END, revisions are treated in reverse order.

A range acts as a closed interval. This means that a range of 3:5
gives 3, 4 and 5. Similarly, a range of 9:6 gives 9, 8, 7, and 6.