pgsql: Add list of ignorable pgindent commits for git-blame.

Add list of ignorable pgindent commits for git-blame.

Add a .git-blame-ignore-revs file with a list of pgindent, pgperlyidy,
and reformat-dat-files commit hashes. Postgres hackers that configure
git to use the ignore file will get git-blame output that avoids
attributing line changes to the ignored indent commits. This makes
git-blame output much easier to work with in practice.

Author: Peter Geoghegan <pg(at)bowt(dot)ie>
Reviewed-By: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Discussion: https://postgr.es/m/CAH2-Wz=cVh3GHTP6SdLU-Gnmt2zRdF8vZkcrFdSzXQ=WhbWm9Q@mail.gmail.com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/8e638845ff6bb255ad1dea15831089a234535391

Modified Files
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.git-blame-ignore-revs | 219 ++++++++++++++++++++++++++++++++++++++++++++++
src/tools/RELEASE_CHANGES | 4 +
src/tools/pgindent/README | 5 ++
3 files changed, 228 insertions(+)