Fixes all deprecated API usage in libs.jgit and update gitignore IO code

[mbien]

first commit:

• remove deprecated jgit api usage
• fixed all other compiler warnings too (edit: only in libs.jgit :))

second commit:

• renovate the git ignore/unignore IO code
• make sure the file specific line separators are retained during file updates

I tested (stepped through it) some of it manually: list/switch branches, list/add/remove tags

lets see what tests say

[mbien]

testLogWithBranchInfoMoreBranches: org.netbeans.libs.git.jgit.commands.LogTest

junit.framework.AssertionFailedError
    at org.netbeans.libs.git.jgit.commands.LogTest.testLogWithBranchInfoMoreBranches(LogTest.java:775)
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:77)
    at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at org.netbeans.junit.NbTestCase.access$200(NbTestCase.java:79)
    at org.netbeans.junit.NbTestCase$2.doSomething(NbTestCase.java:484)
    at org.netbeans.junit.NbTestCase$1Guard.run(NbTestCase.java:405)
    at java.base/java.lang.Thread.run(Thread.java:840)

one test fails, the bug is in ListBranchCommand, since it works when i revert the changes. Going to take a look tomorrow.

[mbien]

refreshed PR, testing this a bit manually and if I don't find anything I will merge once green again

[mbien]

added an extra commit which renovates git ignore/unignore IO code

[matthiasblaesing]

added an extra commit which renovates git ignore/unignore IO code

Would it be possible to detect the line end character of the file and use that on save? I observe, that using the Ignore/Unignore action in NetBeans currently leads to many of my .gitignore files to be completely changed.

[mbien]

@matthiasblaesing I take a look

[mbien]

added tests + refreshed PR