wagon-ssh-external: Use absolute-dir in case localFile.getParentFile returns null

[sgothel]

If using mvn gpg:sign-and-deploy-file as shown below, localFile becomes e.g. gluegen-2.6.0-sources.jar, i.e. relative and w/o parent-directory. Hence localFile.getParentFile() returns null and the previous code fails to transport the file.

mvn -e gpg:sign-and-deploy-file  \
  -DpomFile=pom.xml"             \
  -Dfile=gluegen.jar"            \
  -Dfiles=gluegen-2.6.0-sources.jar,gluegen-2.6.0-javadoc.jar" \
  -Dclassifiers=sources,javadoc" \
  -Dtypes=jar,jar"               \
  -Durl=scpexe://jordan/srv/www/jordan/deployment/maven/ \
  -DrepositoryId=jordan-mirror

This patch uses the localFile.getAbsoluteFile() in case localFile.getParentFile() returns null and renders wagon-ssh-external functional w/ above mvn gpg:sign-and-deploy-file

Tested via mvn install -Dmaven.test.skip and mvn install and JogAmp's maven install scripts at https://jogamp.org/cgit/jogamp-scripting.git/.

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[sgothel]

bump, is this the right channel to ask for a merge? @olamy ?
I surely also like to see this MR cherry picked over to master.

[Copilot]

Pull request overview

This PR fixes a bug where ScpExternalWagon fails when mvn gpg:sign-and-deploy-file is used with relative file paths. When a file is specified as a relative path (e.g., gluegen-2.6.0-sources.jar), the getParentFile() method returns null, causing the original code to fail with a NullPointerException.

Key changes:

• Added null check for localFile.getParentFile() before setting the working directory
• Falls back to using getAbsoluteFile().getParentFile() when the parent is null
• Includes SecurityException handling for the absolute path resolution

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[Copilot]

After obtaining the absolute file, there's still no null check on the second call to getParentFile(). According to Java documentation, getAbsoluteFile().getParentFile() can still return null for filesystem roots (e.g., "/" on Unix or "C:" on Windows). This would cause a NullPointerException on line 243 when calling parentFile.getAbsolutePath(). Consider adding a null check after line 236 and throwing a TransferFailedException with a descriptive message if parentFile is still null.

Suggested change

	}
	}
	if (parentFile == null) {
	TransferFailedException e =
	new TransferFailedException("Cannot determine parent directory of " + localFile);
	fireTransferError(resource, e, put ? TransferEvent.REQUEST_PUT : TransferEvent.REQUEST_GET);
	throw e;
	}

[Copilot]

This change introduces new behavior for handling relative file paths without test coverage. Since the repository already has test files for ScpExternalWagon, consider adding a test case that verifies the behavior when localFile.getParentFile() returns null (e.g., when using a relative path like "gluegen-2.6.0-sources.jar"). This would help ensure the fix works as intended and prevent regressions.