RFR: Improve "git pr help" [v2]

[Magnus Ihse Bursie]

> The help texts were never shown for the "git pr" sub-commands.

Magnus Ihse Bursie has updated the pull request incrementally with one additional commit since the last revision:

  Fix build error
  
  Reviewed-by: ehelin

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Changes:
  - all: https://git.openjdk.java.net/skara/pull/778/files
  - new: https://git.openjdk.java.net/skara/pull/778/files/8603021f..2da6890f

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=skara&pr=778&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=skara&pr=778&range=00-01

  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.java.net/skara/pull/778.diff
  Fetch: git fetch https://git.openjdk.java.net/skara pull/778/head:pull/778

PR: https://git.openjdk.java.net/skara/pull/778