* Upgrate to rails 6.0.0

* Simplify Rails.gitignore

There are a number of OpenSSL-related file extensions (e.g., .pem, .crt,
etc..) that contain data that are generally best not committed to
repositories.  This file contains several common file extensions that
often correlate to these types of files.

.svg files are more often than not vector files. You need to exceed 36 swap files for a .svg file to come from Vim.

* Add esp-idf.gitignore

From https://github.com/espressif/esp-idf-template/blob/master/.gitignore

* Add header comments to esp-idf.gitignore

Newer versions of KiCad call the schematics backup file `.sch-bak`.

* Update Autotools.gitignore

Add ignore-rule for Makefiles generated by configure
(directly by config.status)

* Add some descriptive comment.

Add more descriptive comment to explain why Makefile should be ignore.

* added files to be ignored with swift package manager

* added comment for swiftpm and why it might want to be included in .gitignore

Unlike other packages, TextMesh Pro is not entirely managed by Unity's new Package Manager, and still imports some assets directly into the project.

This new file type can be generated by GHC 8.8.

https://www.haskell.org/ghc/blog/20190626-HIEFiles.html

If you have the [Ionide](http://ionide.io/) tools installed you will get an `.ionide` directory created in each directory that you open with VS Code, regardless of whether or not you are using F#.

The xy package generates *.xyd files whenever the commands

    \MakeOutlines
    \OnlyOutlines
    \ShowOutlines
    \NoOutlines

are present in the LaTeX source. These automatically-generated files
contain the dimensions of figures typeset with xy and are recreated as
needed. This is documented on pp. 15f. of the XY-pic Reference Manual
(1999/02/16).

As automatically-generated, temporary files, they should be ignored.

also, re-ordered some elements to ensure the gitignore is in directory/file and lexicographic order

This reverts commit 6ffcee97.

See also 15e56afe introduced this for Rails.gitignore.

Docs on Sqlite temporary files
https://www.sqlite.org/tempfiles.html#rollback_journals

Thanks @nickittynack (Nick Reynolds)

package not interfere with makeindex's style files

from vim's documentation on `:mksession` (:help :mksession):

 ...

 10. If a file exists with the same name as the Session file, but ending
     in "x.vim" (for eXtra), executes that as well.  You can use *x.vim
     files to specify additional settings and actions associated with a
     given Session, such as creating menu items in the GUI version.

we already have Session.vim ignored.  the Sessionx.vim file, like
Session.vim, is a user file.  a user would generally want that file kept
private or for themselves, and the public or a team fetching from or
sharing the repository generally have no interest in a file relevant
only to a particular user.  so it's a good idea to get git to help us
avoid mistakenly sharing the file.

Actually, the log generated by debug mode is *.log
i.e. ubuntu-xenial-16.04-cloudimg-console.log

When IntelliJ project is created as a file-based (i.e. without `.idea` folder, but with `.iws`, `.iml` and `.ipr` files), and this is a Gradle or Maven project with auto-import, should ignore them as well for the same reason we ignore `.idea` folder content in that case.

* ignore all caches

* ignore release folder

... to let the file point to its canonical source

* Update Node.gitignore

* Fix coverage.lcov to *.lcov

See https://lists.launchpad.net/kicad-developers/msg38339.html and https://lists.launchpad.net/kicad-developers/msg38638.html

When a Unity project is opened in Jetbrains Rider, it installs a editor plugin into the Assets/Plugins/Editor/Jetbrains folder to manage Unity->Rider integration. This plugins life cycle is managed by your local Rider install and is automatically updated by Rider. It should not be committed to source control.  This is documented by Jetbrains here https://www.jetbrains.com/help/rider/Unity.html

This change should ignore both the Jetbrains plugin folder and its .meta file correctly. For completeness, it would be nice to also ignore the /.idea*/ settings folder that Rider autogenerates, but i see a PR implementing that change has already been rejected.