multi-wc-format: svn_wc__format_from_version()

[Daniel Shahaf]

Here's the docstring:

[[[
/**
 * Convert @a version to that version's characteristic working copy
 * format, returned in @a format.
 *
 * A NULL @a version translates to the library's default version.
 ⋮
 */
svn_error_t *
svn_wc__format_from_version(int *format,
                            const svn_version_t* version,
                            apr_pool_t *scratch_pool);
]]]

Here's part of the implementation:

[[[
  switch (version->minor)
    {
      case 0:  /* Same as 1.3.x. */
      case 1:  /* Same as 1.3.x. */
      case 2:  /* Same as 1.3.x. */
      case 3:  *format = 4; break;
      case 4:  *format = 8; break;
      case 5:  *format = 9; break;
      case 6:  *format = 10; break;
      case 7:  *format = 29; break;
      case 8:  /* Same as 1.14.x. */
      case 9:  /* Same as 1.14.x. */
      case 10: /* Same as 1.14.x. */
      case 11: /* Same as 1.14.x. */
      case 12: /* Same as 1.14.x. */
      case 13: /* Same as 1.14.x. */
      case 14: *format = 31; break;
      case 15: /* Same as the current version. */
      default: *format = SVN_WC__VERSION; break;
    }

  return SVN_NO_ERROR;
]]]

What does the term "characteristic" mean?  Is it the oldest, newest, or
default wc format supported by @a version?

The implementation uses the newest, but that may have been an oversight
(cf. r1899000), and it's not clear to me from the callers what they
expect.

Cheers,

Daniel