Diff & Merge
On this page, specify the default behavior of the Differences viewer.
Use the slider to specify the amount of context lines that will not collapse, when in a Differences viewer you click the button to collapse the unchanged fragments.
Go to the next file after reaching last change
If this checkbox is selected, IntelliJ IDEA will suggest to click F7/Shift+F7 once more and compare other files
Automatically apply non-conflicting changes
If this checkbox is selected, the interactive merge tool automatically merges all non-conflicting changes.
This is an equivalent to clicking in the Merge dialog.
Highlight modified lines in gutter
Select this checkbox if you want added/modified lines (relative to the base revision) to be highlighted in the gutter of the Merge dialog.