What to gitignore from the .idea folder?
I just want to present a more recent alternative. There is an online tool that generates .gitignore files based on operating systems, IDEs and programming languages that you might be using.
gitignore.io
EDIT Disclaimer: Do not copy this file, copy the file generated by the website instead, they do a good job on keeping it updated. This is just an example.
The file generated for IntelliJ contains the following
# Created by https://www.gitignore.io/api/intellij
### Intellij ###
# Covers JetBrains IDEs: IntelliJ, RubyMine, PhpStorm, AppCode, PyCharm, CLion, Android Studio and Webstorm
# Reference: https://intellij-support.jetbrains.com/hc/en-us/articles/206544839
# User-specific stuff:
.idea/workspace.xml
.idea/tasks.xml
.idea/dictionaries
.idea/vcs.xml
.idea/jsLibraryMappings.xml
# Sensitive or high-churn files:
.idea/dataSources.ids
.idea/dataSources.xml
.idea/dataSources.local.xml
.idea/sqlDataSources.xml
.idea/dynamic.xml
.idea/uiDesigner.xml
# Gradle:
.idea/gradle.xml
.idea/libraries
# Mongo Explorer plugin:
.idea/mongoSettings.xml
## File-based project format:
*.iws
## Plugin-specific files:
# IntelliJ
/out/
# mpeltonen/sbt-idea plugin
.idea_modules/
# JIRA plugin
atlassian-ide-plugin.xml
# Crashlytics plugin (for Android Studio and IntelliJ)
com_crashlytics_export_strings.xml
crashlytics.properties
crashlytics-build.properties
fabric.properties
### Intellij Patch ###
# Comment Reason: https://github.com/joeblau/gitignore.io/issues/186#issuecomment-215987721
# *.iml
# modules.xml
https://www.gitignore.io/api/jetbrains
Created by https://www.gitignore.io/api/jetbrains
### JetBrains ###
# Covers JetBrains IDEs: IntelliJ, RubyMine, PhpStorm, AppCode, PyCharm, CLion, Android Studio and Webstorm
# Reference: https://intellij-support.jetbrains.com/hc/en-us/articles/206544839
# User-specific stuff:
.idea/workspace.xml
.idea/tasks.xml
.idea/dictionaries
.idea/vcs.xml
.idea/jsLibraryMappings.xml
# Sensitive or high-churn files:
.idea/dataSources.ids
.idea/dataSources.xml
.idea/dataSources.local.xml
.idea/sqlDataSources.xml
.idea/dynamic.xml
.idea/uiDesigner.xml
# Gradle:
.idea/gradle.xml
.idea/libraries
# Mongo Explorer plugin:
.idea/mongoSettings.xml
## File-based project format:
*.iws
## Plugin-specific files:
# IntelliJ
/out/
# mpeltonen/sbt-idea plugin
.idea_modules/
# JIRA plugin
atlassian-ide-plugin.xml
# Crashlytics plugin (for Android Studio and IntelliJ)
com_crashlytics_export_strings.xml
crashlytics.properties
crashlytics-build.properties
fabric.properties
### JetBrains Patch ###
# Comment Reason: https://github.com/joeblau/gitignore.io/issues/186#issuecomment-215987721
# *.iml
# modules.xml
# .idea/misc.xml
# *.ipr
The official support page should answer your question.
So in your .gitignore you might ignore the files ending with .iws, and the workspace.xml and tasks.xml files.
For a couple of years I was a supporter of using a specific .gitignore for IntelliJ with this suggested configuration.
Not anymore.
IntelliJ is updated quite frequently, internal config file specs change more often than I would like and JetBrains flagship excels at auto-configuring itself based on maven/gradle/etc build files.
So my suggestion would be to leave all editor config files out of project and have users configure editor to their liking. Things like code styling can and should be configured at build level; say using Google Code Style or CheckStyle directly on Maven/Gradle/sbt/etc.
This ensures consistency and leaves editor files out of source code that, in my personal opinion, is where they should be.