A terser .gitignore file. (#6324)

* A terser .gitignore file.

I trimmed _.gitignore_ to the stuff that looked like it was still useful
(at least, to me). Most of what's in there seemed like remnants of
previous build systems (Buck, Stack, etc.). Other stuff includes
editor-specific configuration files, which you can add to your global
_.gitignore_ (`git config --global core.excludesfile ~/.gitignore`).

I left the macOS _.DS_Store_ files in, even though I believe they should
also go into your global, machine-specific _.gitignore_ file, because
eventually someone's going to check them in otherwise.

On my machine, this has exactly the same effect as the longer one.
However, it's highly likely that I've overlooked something; let me know
and I can add it back.

CHANGELOG_BEGIN
CHANGELOG_END

* Add editors back into the .gitignore file.

I guess we really don't want people checking these files in by accident.

.gitignore

@@ -1,97 +1,64 @@
-.DS_Store
-._.DS_Store
-.stack-work
-pkgs/*/.stack-work
-workspaces/*/.stack-work
-distribution-work
-.idea
+# private configuration
 .envrc.private
-*.iml
-*.ipr
-*.iws
-.*.sw?
-.sw?
-*.pyc
-*.o
-*.hi
-dist/
-cache/
-target/
-target-sbt/
-build/
-result
-.project
-.build
-/ci-out/
-**/codex.tags
-/hscope.out
-._thesis.pdf
-\#*\#
-.\#*\#
-*.tix
-.da-*-gui-state
-/pkgs/generated
-TAGS
-tags
-/result-*
-**/.settings
-**/.classpath
-**/.factorypath
-*.tgz
-*.tar.gz
-ghc-bindist
-*.result.xml
-**/.ensime
-**/.ensime_cache
-ensime.sbt
-pipelinePerformance.xml
-**/database_test.manifest
-.ghci
-.ghcid
+
+# Log files
 *.log
-.buckd
-buck-out
-.buckconfig.local
-haskell-style-check.txt
-da-daml-equities-library.txt
-*.egg-info/
-.flattened-pom.xml
-*~
-*.orig
-venv
-trace.*.dat
-node_modules/
-/out/
-.hpc
-hpc-report/
-/results
-**/latency.csv
-**/summary-report.txt
-.scannerwork/
-**/dump-*.txt
-**/*tests.xml
-ledger-api/.bin
-*.db
-.vscode
-.m2/
-.history/
-**/.history/
-### Bazel: https://www.gitignore.io/api/bazel ###
+
+# DAML
+.daml/
+
+# dev-env
+/dev-env/var/
+
+# Bazel
+/.bazel-cache/
 /bazel-*
 /compatibility/bazel-*
 /compatibility/.bazelrc
 /compatibility/head_sdk/
 .bazelrc.local
-.ijwb
 .bazelproject
-.bazel-cache
-.rattle
-daml-lf/project
-daml-lf/gen
-daml-lf/build.sbt
-.markdown-preview.html
-compiler/damlc/output
-language-support/hs/bindings/gen
-language-support/hs/bindings/*.cabal
-language-support/hs/bindings/examples/nim/*.cabal
-.daml/
+
+# node.js
+node_modules/
+
+
+### Operating Systems ###
+
+# macOS
+.DS_Store
+._.DS_Store
+
+
+### Editors ###
+
+# Eclipse
+.classpath
+.factorypath
+.project
+.settings
+
+# Emacs
+\#*\#
+.\#*\#
+*~
+
+# Ensime
+.ensime
+.ensime_cache
+
+# IntelliJ IDEA
+.idea
+.ijwb # Bazel
+*.iml
+*.ipr
+*.iws
+out
+
+# Vim
+*~
+*.swo
+*.swp
+
+# Visual Studio Code
+.vscode