doc: Fix whitespace errs in .md files, bitcoin.conf, and Info.plist.in #16812

Although there is an existing test/lint/lint-whitespace.sh linter, it only prevents new errors from being introduced. This commit removes all existing whitespace errors from Core markdown files (skips src/crypto/ctaes/, leveldb/, and doc/release-notes/), bitcoin.conf, and Info.plist.in.

Further formatting could be done on the markdown documents, but seeing as there several coexisting styles that break a few markdownlint rules, a first step would be to define and add a linter to Travis. For now, the small fix is made.

Concept ACK

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Conflicts

Reviewers, this pull request conflicts with the following ones:

• #16392 (WIP build: macOS toolchain update by fanquake)

If you consider this pull request important, please also help to review the conflicting pull requests. Ideally, start with the one that should be merged first.

The script doesn't run on Travis:

Running script for: ac5b890fb1b05fc2d8df7e876fa94d045bf6fbc0
shopt -s globstar
sed -i 's/[ 	]*$//g' {build_msvc,ci,contrib,depends,test}/*.md doc/*.{md,txt} contrib/**/*.{md,txt} share/**/*.{conf,plist.in,md} test/**/*.md
test/lint/commit-script-check.sh: 1: eval: shopt: not found
sed: can't read {build_msvc,ci,contrib,depends,test}/*.md: No such file or directory
sed: can't read doc/*.{md,txt}: No such file or directory
sed: can't read contrib/**/*.{md,txt}: No such file or directory
sed: can't read share/**/*.{conf,plist.in,md}: No such file or directory

For some reason, the script is skipping build-aux/ in Travis, which accounts for a single correction. I've tried it with and without both quotes and escaped dash. It runs correctly on all my linux environments - is there a bashism I'm missing?

Could remove the touch to the .m4 file, instead, but it would be nice to get this scripted-diff working. Inspired by @promag's https://github.com/bitcoin/bitcoin/commit/12dd1013454a3b4913e8e6bbac251887e7e82ff0

Edit: Final script was:

-BEGIN VERIFY SCRIPT-
sed -i -r 's/[ \t]*$//g' \
$(git grep -IlE '[ \t]*$' -- \
build_msvc/*.{md,in,sln,vcxproj} \
"build-aux"/m4/*.m4 \
ci/*.md \
ci/**/*.md \
contrib/*.{"bash-completion",md,pro,supp} \
contrib/**/*.{cfg,in,md,plist,scm,txt,yml} \
depends/*.{md,mk} \
depends/**/*.{md,mk} \
doc/*.{in,md,txt} \
share/*.in \
share/**/*.{conf,in,md,txt} \
src/**/*.md \
test/*.md \
test/**/*.{in,md} \
':!src/crypto/ctaes' \
':!src/leveldb' \
':!src/secp256k1' \
':!src/univalue' \
)
-END VERIFY SCRIPT-

Concept ACK.

To be honest I'm not really concerned about the scripted diff here. A single commit that removes the last of the (impossible to re-introduce) whitespace should be fine.

ACK 48cef93ea1ca59f55f001c2c3ea122280bb05e0f -- diff looks correct

Can the scripted diff be removed, then?

Removed.

ACK 6aab7649d30b19d136a27f1287fd2c8b00fb460c - Thanks for following up. Hopefully we now never have to deal with whitespace again.