I add to a .gitignore file the line :
nbproject\

Then occurs and exception :
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SEVERE [org.openide.util.RequestProcessor]: Error in RequestProcessor org.netbeans.modules.git.ui.commit.GitCommitPanel$GitCommitDialogProgressSupport
java.util.regex.PatternSyntaxException: Unexpected internal error near index 10
nbproject\
          ^
	at java.util.regex.Pattern.error(Pattern.java:1955)
	at java.util.regex.Pattern.compile(Pattern.java:1702)
	at java.util.regex.Pattern.<init>(Pattern.java:1351)
	at java.util.regex.Pattern.compile(Pattern.java:1028)
	at org.eclipse.jgit.ignore.internal.Strings.convertGlob(Strings.java:352)
	at org.eclipse.jgit.ignore.internal.WildCardMatcher.<init>(WildCardMatcher.java:66)
	at org.eclipse.jgit.ignore.internal.PathMatcher.createNameMatcher0(PathMatcher.java:145)
	at org.eclipse.jgit.ignore.internal.PathMatcher.createPathMatcher(PathMatcher.java:127)
	at org.eclipse.jgit.ignore.FastIgnoreRule.<init>(FastIgnoreRule.java:114)
	at org.eclipse.jgit.ignore.IgnoreNode.parse(IgnoreNode.java:114)
	at org.eclipse.jgit.treewalk.WorkingTreeIterator$PerDirectoryIgnoreNode.load(WorkingTreeIterator.java:1166)
	at org.eclipse.jgit.treewalk.WorkingTreeIterator$RootIgnoreNode.load(WorkingTreeIterator.java:1187)
	at org.eclipse.jgit.treewalk.WorkingTreeIterator.getIgnoreNode(WorkingTreeIterator.java:625)
	at org.eclipse.jgit.treewalk.WorkingTreeIterator.isEntryIgnored(WorkingTreeIterator.java:593)
	at org.eclipse.jgit.treewalk.WorkingTreeIterator.isEntryIgnored(WorkingTreeIterator.java:576)
	at org.eclipse.jgit.treewalk.WorkingTreeIterator.isEntryIgnored(WorkingTreeIterator.java:563)
	at org.netbeans.libs.git.jgit.commands.StatusCommand.run(StatusCommand.java:205)
	at org.netbeans.libs.git.jgit.commands.GitCommand$1.run(GitCommand.java:80)
	at org.netbeans.libs.git.jgit.commands.GitCommand$1.run(GitCommand.java:77)
	at java.security.AccessController.doPrivileged(Native Method)
	at org.netbeans.libs.git.jgit.commands.GitCommand.execute(GitCommand.java:77)
	at org.netbeans.libs.git.GitClient.getStatus(GitClient.java:760)
	at org.netbeans.modules.git.client.GitClient$26.call(GitClient.java:500)
	at org.netbeans.modules.git.client.GitClient$26.call(GitClient.java:496)
	at org.netbeans.modules.git.client.GitClient$CommandInvoker$1$1.call(GitClient.java:956)
	at org.netbeans.modules.git.client.GitClient$CommandInvoker$1.call(GitClient.java:979)
	at org.netbeans.modules.git.client.GitClient$CommandInvoker.runMethodIntern(GitClient.java:991)
	at org.netbeans.modules.git.client.GitClient$CommandInvoker.runMethod(GitClient.java:920)
	at org.netbeans.modules.git.client.GitClient$CommandInvoker.access$300(GitClient.java:892)
	at org.netbeans.modules.git.client.GitClient.getStatus(GitClient.java:496)
	at org.netbeans.modules.git.client.GitClient.getStatus(GitClient.java:492)
	at org.netbeans.modules.git.FileStatusCache.refreshAllRoots(FileStatusCache.java:233)
	at org.netbeans.modules.git.ui.commit.GitCommitPanel$GitCommitDialogProgressSupport.loadFiles(GitCommitPanel.java:292)
	at org.netbeans.modules.git.ui.commit.GitCommitPanel$GitCommitDialogProgressSupport.perform(GitCommitPanel.java:255)
	at org.netbeans.modules.git.client.GitProgressSupport.performIntern(GitProgressSupport.java:115)
	at org.netbeans.modules.git.client.GitProgressSupport.run(GitProgressSupport.java:108)
	at org.openide.util.RequestProcessor$Task.run(RequestProcessor.java:1443)
	at org.netbeans.modules.openide.util.GlobalLookup.execute(GlobalLookup.java:68)
	at org.openide.util.lookup.Lookups.executeWith(Lookups.java:303)
	at org.openide.util.RequestProcessor$Processor.run(RequestProcessor.java:2058)
Caused: org.openide.util.RequestProcessor$SlowItem: task failed due to
	at org.openide.util.RequestProcessor.post(RequestProcessor.java:420)
	at org.netbeans.modules.git.client.GitProgressSupport.start(GitProgressSupport.java:101)
	at org.netbeans.modules.git.ui.commit.GitCommitPanel.computeNodesIntern(GitCommitPanel.java:217)
	at org.netbeans.modules.git.ui.commit.GitCommitPanel.computeNodes(GitCommitPanel.java:182)
	at org.netbeans.modules.versioning.util.common.VCSCommitPanel.open(VCSCommitPanel.java:613)
	at org.netbeans.modules.git.ui.commit.GitCommitPanel.open(GitCommitPanel.java:189)
	at org.netbeans.modules.git.ui.commit.CommitAction$1.run(CommitAction.java:154)
	at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:311)
	at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:756)
	at java.awt.EventQueue.access$500(EventQueue.java:97)
	at java.awt.EventQueue$3.run(EventQueue.java:709)
	at java.awt.EventQueue$3.run(EventQueue.java:703)
	at java.security.AccessController.doPrivileged(Native Method)
	at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:76)
	at java.awt.EventQueue.dispatchEvent(EventQueue.java:726)
	at org.netbeans.core.TimableEventQueue.dispatchEvent(TimableEventQueue.java:159)
	at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:201)
	at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:116)
	at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:105)
	at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:101)
	at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:93)
[catch] at java.awt.EventDispatchThread.run(EventDispatchThread.java:82)
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Product Version: NetBeans IDE Dev (Build 201610260002)
Java: 1.8.0_101; Java HotSpot(TM) 64-Bit Server VM 25.101-b13
Runtime: Java(TM) SE Runtime Environment 1.8.0_101-b13
System: Windows 10 version 10.0 running on amd64; Cp1252; fr_FR (nb)
User directory: C:\Users\Anael\AppData\Roaming\NetBeans\dev
Cache directory: C:\Users\Anael\AppData\Local\NetBeans\Cache\dev