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.

Netbeans Linux and Windows Makefile-*.mk and Package-*.bash files in nbproject directories are automatically generated during compile.  These files are continually updated, which can cause a long list of unnecessary files to add, commit, and push (or that are Untracked).  This has been experienced for Linux and Windows C++ projects.  Helpful supporting link: https://stackoverflow.com/questions/27490608/netbeans-c-and-git

Refs: http://network-security.data

See this SO post: https://stackoverflow.com/questions/49557737/should-i-add-idea-caches-build-file-checksums-ser-to-gitignore

and this Google issue tracker ticket: https://issuetracker.google.com/issues/77544553

for justification.

If checked the option "Always create backup copy" under Settings -> Save within Microsoft Word 2016 on macOS, when editing a docx file, a folder named as same as docx file name(without ext) will be created and placed a docx backup file named "Backup of DOCX_ORIGINAL_FILENAME.docx".

contentModel.xml is automatically generated and can be safely ignored.

Source: https://rider-support.jetbrains.com/hc/en-us/community/posts/115000661950-A-lot-of-files-in-contentModel-xml?page=1#community_comment_115000538984

Updating file to match the one for swift and objective c.

Add extra commented section to use when using Gradle or Maven auto-import.
These are mentioned in the original reference for optional excludes (https://intellij-support.jetbrains.com/hc/en-us/articles/206544839).
If this would be better as a separate, non-commented ignore file, let me know and I will resubmit.

.idea/misc.xml used to contain usage statistics.  This was broken out to usage.statistics.xml in the latest EAP (2018.2 EAP).  It should be excluded from git.

See https://youtrack.jetbrains.com/issue/IDEA-192913

ignore dbnavigator.xml

because it contains sensitive data, such as host, port, db, user name, and so on.

Microsoft was announced a new extension of installer for Windows. I just added that one to be ignored as default, like others installers files.
References:
https://blogs.windows.com/buildingapps/2018/03/07/three-things-need-know-windows-developer-day/
https://github.com/Microsoft/msix-packaging

This directory used by HTTP Client in IntelliJ IDEA (and other product).
https://www.jetbrains.com/help/idea/http-client-in-product-code-editor.html#viewingResponse

Since IDEA 14 (2014), IDEA and other contemporaneous JebBrains IDEs don't store sensitive info in `datasources.xml` and it makes sense to version control to share project data sources among the team. `dataSources.local.xml` is user-specific: contain usernames and could be sensitive from a security perspective, albeit passwords could be externalized to e.g. Mac Keychain.

References: https://intellij-support.jetbrains.com/hc/en-us/articles/206544839, https://youtrack.jetbrains.com/issue/IDEA-127105

On line 1, WebStorm is capitalized the same way as the other IDE names.