pgsql: initdb: Add --no-sync-data-files.

initdb: Add --no-sync-data-files.

This new option instructs initdb to skip synchronizing any files
in database directories, the database directories themselves, and
the tablespace directories, i.e., everything in the base/
subdirectory and any other tablespace directories. Other files,
such as those in pg_wal/ and pg_xact/, will still be synchronized
unless --no-sync is also specified. --no-sync-data-files is
primarily intended for internal use by tools that separately ensure
the skipped files are synchronized to disk. A follow-up commit
will use this to help optimize pg_upgrade's file transfer step.

The --sync-method=fsync implementation of this option makes use of
a new exclude_dir parameter for walkdir(). When not NULL,
exclude_dir specifies a directory to skip processing. The
--sync-method=syncfs implementation of this option just skips
synchronizing the non-default tablespace directories. This means
that initdb will still synchronize some or all of the database
files, but there's not much we can do about that.

Discussion: https://postgr.es/m/Zyvop-LxLXBLrZil%40nathan

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/cf131fa942855acd42e8283185837566c7e8c15e

Modified Files
--------------
doc/src/sgml/ref/initdb.sgml | 27 +++++++++
src/bin/initdb/initdb.c | 10 +++-
src/bin/initdb/t/001_initdb.pl | 1 +
src/bin/pg_basebackup/pg_basebackup.c | 2 +-
src/bin/pg_checksums/pg_checksums.c | 2 +-
src/bin/pg_combinebackup/pg_combinebackup.c | 2 +-
src/bin/pg_rewind/file_ops.c | 2 +-
src/common/file_utils.c | 85 +++++++++++++++++++----------
src/include/common/file_utils.h | 2 +-
9 files changed, 96 insertions(+), 37 deletions(-)