On Wed, 27 Sep 2017 13:09:42 -0400
Jeff Hostetler <git@xxxxxxxxxxxxxxxxx> wrote:
> On 9/26/2017 6:39 PM, Jonathan Tan wrote:
> > On Fri, 22 Sep 2017 20:30:11 +0000
> > Jeff Hostetler <git@xxxxxxxxxxxxxxxxx> wrote:
> >
> >> Makefile | 1 +
> >> object-filter.c | 269 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++
> >> object-filter.h | 173 ++++++++++++++++++++++++++++++++++++
> >> 3 files changed, 443 insertions(+)
> >> create mode 100644 object-filter.c
> >> create mode 100644 object-filter.h
> >
> > I think these and list-objects-filter-* are multiple levels of
> > indirection too many. Would a single file with a few implementations of
> > filter_object_fn be sufficient?
>
> I did that in my first draft and I found it confusing.
>
> Each filter has 3 parts (some filter-specific data structures,
> a filter callback routine, a driver to call the traverse code).
> I found it easier to reason about each filter in isolation.
> And it makes it easier to work on each independently and keep
> their inclusion in separate commits.
I looked at object-filter.{c,h} a bit more. It seems that these files:
1) define a struct that contains all the options that we would want
2) supplies a way to populate this struct from code that uses parse-options
3) supplies a way to populate this struct from code that calculates
options by hand
4) supplies a way to populate this struct from "protocol" ("<key>" or
"<key> <value>" strings)
And the next commit takes the struct that object-filter.{c,h} produces
and actually performs the traversal.
I think this can be significantly simplified, though. Would this work:
a) Define the object_filter_options struct, but make all fields
correspond to a single parameter each. Define
OBJECT_FILTER_OPTIONS_INIT to initialize everything to 0 except for
large_byte_limit to ULONG_MAX (so that we can detect if something
else is set to it).
b) Define one single OPT_PARSE_FILTER macro containing all the
parameters. We can use the non-callback macros here. That solves 2)
above.
c) Define a function that takes in (int *argc, char ***argv) that can
"massage" it to remove all filter-related arguments, storing them in
a object_filter_options struct. That solves 3) above. As discussed
in the API documentation, this means that argument lists of the form
"--unknown --known" (where "--unknown" takes an argument) are
processed differently, but then again, rev-list never supported them
anyway (it required "--unknown=<arg>").
d) Define a function that converts "<key>" into "--<key>" and "<key>
<value>" into "--<key>=<value>", and use the existing mechanism.
That solves 4) above.
This removes the need to maintain the lists of one-per-argument
functions, including the parse_filter_* and opt_parse_filter_* functions
declared in the header file. If we were to add a feature, we wouldn't
need to change anything in the caller, and wouldn't need to hand-edit
object_filter_hand_parse_arg() and object_filter_hand_parse_protocol().
