[Gnu-arch-users] names -> tagline method transition

[Michael Teichgräber]

Hello,

when turning an old project from id-tagging-method `names' to
`tagline' I wondered if it would be possible to minimize the changes
caused by this action.

As ids for files in a `names' tree are composed by

   str_alloc_cat (limits, "?", as_file)

and ids for untagged files in a `tagline' tree by

   str_alloc_cat (limits, "?_", as_file)

the transition will recognize most files as deleted+added. Would it
have drawbacks to treat ids beginning with "?_" and "?" as the same
when calculating changes?



A different thing is that files within the {arch} directory get
"?..."-style ids in a `names' tree, while they are assigned
"A_..."-style ids in a `tagline' tree. This causes files within {arch}
get deleted+added as well, though they always stay the same.

By moving the `if (method == ftag_names)' block in inv-ids.c behind
the `is_at_or_underneath_archdir (as_file)' test, it is possible to
use "A_..." ids in `names' trees to. Users working on `names' trees
would have to recreate the corresponding library (because of index
differences) and for some edge-cases perhaps face problems when
applying certain changesets.


With this change and a hack for the first case above I was able to
narrow the list of changed files in a names->tagline transition to
"{arch}/=tagging-method". Would such a change in tla be worth the
effort, or rather not, since such transitions will rarely occur?


-- 
Michael