devtools: Always use unabbreviated commit IDs in github-merge.py #16201

Always put the unabbreviated commit IDs in the generated commit messages and other places. This prevents the developer's core.abbrev git setting from leaking through and is better against ambiguity too.

ACK 067fba56314f399674dd471c663e663040be52a3 (replaces h with H, didn't test)

ACK 067fba56314f399674dd471c663e663040be52a3, from the documentation https://git-scm.com/docs/pretty-formats:

Placeholders that expand to information extracted from the commit:

'%H' commit hash

'%h' abbreviated commit hash

ACK https://github.com/bitcoin/bitcoin/pull/16201/commits/067fba56314f399674dd471c663e663040be52a3. Tested by merging this PR into master, then merging a second PR ontop and checking that full commit hashes were being used. Also checked documentation linked to above. Did not check that this works when a different core.abbrev is set locally.

contrib/devtools/github-merge.py 16201
[pull/16201/local-merge d9b6e6c3c] Merge [#16201](/bitcoin-bitcoin/16201/): devtools: Always use unabbreviated commit IDs in github-merge.py
 Date: Fri Jun 14 11:14:51 2019 +0800
[#16201](/bitcoin-bitcoin/16201/) devtools: Always use unabbreviated commit IDs in github-merge.py into master
* 067fba563 devtools: Always use unabbreviated commit IDs in github-merge.py (Wladimir J. van der Laan) (pull/16201/head)

Dropping you on a shell so you can try building/testing the merged source.
Run 'git diff HEAD~' to show the changes being merged.
Type 'exit' when done.

bash-3.2$ contrib/devtools/github-merge.py 16202
[pull/16202/local-merge 4dac2bcb0] Merge [#16202](/bitcoin-bitcoin/16202/): Refactor network message deserialization
 Date: Fri Jun 14 11:15:46 2019 +0800
[#16202](/bitcoin-bitcoin/16202/) Refactor network message deserialization into master
* 3fa744df9d8db26953b3a17520d5698f94f0cf34 Use adapter pattern for the network deserializer (Jonas Schnelli) (pull/16202/head)
* 24e58210b0dd4b7f41842deebd928104a493c2cb Remove transport protocol knowhow from CNetMessage / net processing (Jonas Schnelli)
* 2d3ae443e268d5b039d422c896f0dc6a146a1be5 Refactor: split network transport deserializing from message container (Jonas Schnelli)

Dropping you on a shell so you can try building/testing the merged source.
Run 'git diff HEAD~' to show the changes being merged.
Type 'exit' when done.