Consistency between 'update' and 'switch' APIs

Intuitively I expect 'update' and 'switch' APIs to be the same except for their essential differences which are:

  - 'update' changes rev; 'switch' changes rev and URL.

  - 'switch' switches every node in the tree to a child of the same URL; 'update' changes only the revision of each node, leaving any switched subtrees switched, so it isn't the same as switching to the current URL.

And possibly one other difference: 'svn update --set-depth=x [--parents]' is used to prune a tree or to extend a tree that was previously excluded or shallow.  'switch' also supports the '--set-depth' option, but not the '--parents' options, so perhaps it is not intended to fully support this usage, or is the lack of '--parents' just incidental?

Some APIs currently have extra parameters that are specific to one or the other:

svn_ra_do_update2(..., pool)
svn_ra_do_switch3(..., ignore_ancestry, ..., result_pool, scratch_pool)

  - switch3() is recently revised from switch2(), specifically to add the 'ignore_ancestry' option to allow it to *not* ignore ancestry.  Previously switch2() always ignored ancestry while update2() did not, so this is a step towards consistency.  Further consistency would be attained by providing the option to update as well.

svn_wc__get_update_editor(..., adds_as_modification, clean_checkout, ...)
svn_wc__get_switch_editor(...)

  - These APIs are the 1.8 replacements for deprecated svn_wc_get_{update,switch}_editor4().

  - 'clean_checkout' appears to be just an optimisation hint to bypass some unnecessary checks when we're
using 'update' to do a checkout, and as such it doesn't need to be
available in 'switch'.

  - 'adds_as_modification' controls whether a tree conflict is raised for an incoming add onto a local add, and makes just as much sense for 'switch' as for 'update'.

svn_client__update_internal(..., adds_as_modification, make_parents, ...)
svn_client__switch_internal(..., ignore_ancestry, ...)
svn_client_update4(..., adds_as_modification, make_parents, ...)
svn_client_switch3(..., ignore_ancestry, ...)

  - 'adds_as_modification' and 'ignore_ancestry' are as described above.

  - I'm not sure whether 'make_parents' would make sense for 'switch'.

PROPOSAL

  - svn_ra_do_update2(): revise to svn_ra_do_update3(), add the
'ignore_ancestry' option there too, and use two pools while we're at
it.  Track this change in the RA vtable 'update' method, protocols, etc.

  - svn_wc__get_switch_editor(): add 'adds_as_modification'.

  - svn_client__update_internal(), svn_client_update4(): add 'ignore_ancestry'.

  - svn_client__switch_internal(), svn_client_switch4(): add 'adds_as_modification'.

RATIONALE

Do I really have to explain why Consistency is Good?

Thoughts?

- Julian

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