[MacPorts] #59696: redundant depends_fetch on port:git OR just use the port everywhere

[MacPorts]

#59696: redundant depends_fetch on port:git OR just use the port everywhere
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 Reporter:  RJVB         |      Owner:  (none)
     Type:  enhancement  |     Status:  new
 Priority:  Normal       |  Milestone:
Component:  base         |    Version:
 Keywords:               |       Port:
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 I just noticed that a number of VCS fetch methods get the command from the
 system, possibly if it meets certain requirements. No account is made for
 this in the fetch dependencies: ports using fetch.type set to git or to
 bzr still inherit a depends_fetch on the corresponding port.

 Curiously, the git and svn commands are taken from the system when not
 running on Darwin. I'd do the opposite, take them from $prefix ... at
 least in an installation that is actually supposed to be usable. On any
 other Unix than Darwin the same consideration applies that MacPorts could
 be used to install newer versions of utilities and libraries than those
 provided by the distribution (case in point: my Ubuntu's git command fails
 with invent.kde.org while port:git succeeds just fine).

 It would probably also be fine to have a lazy dependency on the MacPorts
 versions of the VCS types that are recent enough in the system, that is,
 use the version from $prefix if it exists, instead of the system version.

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Ticket URL: <https://trac.macports.org/ticket/59696>
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