[tor-bugs] #21449 [Core Tor/Tor]: Make tor version parsing and version spec consistent

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#21449: Make tor version parsing and version spec consistent
------------------------------+------------------------------
     Reporter:  teor          |      Owner:
         Type:  defect        |     Status:  new
     Priority:  Medium        |  Milestone:  Tor: unspecified
    Component:  Core Tor/Tor  |    Version:
     Severity:  Normal        |   Keywords:  tor-spec
Actual Points:                |  Parent ID:
       Points:  2             |   Reviewer:
      Sponsor:                |
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 In tor_version_compare, the git logic is a bit weird, because git tags are
 hashes: the ordering we apply isn't their true order. So the function
 comment should probably become:

 {{{
 /** Compare two tor versions; Return <0 if a < b; 0 if a ==b, >0 if a >
 * b. Git tags are sorted by length, then value. */
 }}}

 But this doesn't match version-spec.txt:

 {{{
 The EXTRA_INFO is also purely informational, often containing information
 about the SCM commit this version came from. It is surrounded by
 parentheses
 and can't contain whitespace. Unlike the STATUS_TAG this never impacts the
 way
 that versions should be compared.
 }}}

 We should try to ignore the git tag, or at least be very careful how we
 compare it. Due to bugs like #20492, the following versions are
 equivalent:
 {{{
 Tor 0.2.9.9 (git-56788a2489127072)
 Tor 0.2.9.9
 }}}

 (But these are not equivalent to any other git tag on Tor 0.2.9.9, which
 should never happen anyway.)

 This is important when we try to exclude versions, like in #20509, because
 we need to exclude the version with and without the git tag.

 This fix might require a new consensus method.

--
Ticket URL: <https://trac.torproject.org/projects/tor/ticket/21449>
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