bad .git matcher in .project's filteredResources causes chaos

[fbricon]

jdt.ls adds resource filters to .project files, one of those filters matching .git. This caused me to lose several hours trying to figure out why https://github.com/tesla/m2eclipse-egit wasn't compiling in Eclipse, after opening it once in vscode.

.git matches folders like foo.egit, causing classes in subfolders to be entirely ignored by the compiler. Attached demo.zip project shows how bad that is:

The fix seems to be escaping .git as \.git. But even manual fixes are then overridden after a server restart.

[rgrunber]

It comes from : https://github.com/eclipse/eclipse.jdt.ls/blob/5b05202dfaa9777765743df3cd84293b2055add5/org.eclipse.jdt.ls.core/src/org/eclipse/jdt/ls/core/internal/preferences/Preferences.java#L609

It's used in https://github.com/eclipse/eclipse.jdt.ls/blob/5b05202dfaa9777765743df3cd84293b2055add5/org.eclipse.jdt.ls.core/src/org/eclipse/jdt/ls/core/internal/managers/ProjectsManager.java#L545-L577

The configurable setting is java.project.resourceFilters so we can definitely adjust the default.

[rgrunber]

Also for the sake of diagnosing this, org.eclipse.core.resources.regexFilterMatcher makes it clear that we should be escaping the dots.

https://github.com/eclipse-platform/eclipse.platform/blob/3a8770d6bd5bc13ed68086696aa6dd1a9cd8228d/resources/bundles/org.eclipse.core.resources/plugin.xml#L210-L217

https://github.com/eclipse-platform/eclipse.platform/blob/3a8770d6bd5bc13ed68086696aa6dd1a9cd8228d/resources/bundles/org.eclipse.core.resources/src/org/eclipse/core/internal/resources/RegexFileInfoMatcher.java#L48