#498: resolve variables on load #691: solve sub-node merging

[hohwille]

fixes #498 and fixes #691

• fixed variable resolution bug
• resolve variables directly after loading XML (Improvement of XML merger: resolve before merge #498)
• completely refactored XmlMerger (avoid Wrappers for Element and Attr, avoid mutation of template XML)
• smart fallbacks for merge:id
• added caching of first merge:id per QName
• changed fallback for merge:strategy to combine as this is the only default that makes sense
• fixed several bugs
• solved sub-node merging issue for Intellij problems (XMLMerger can not handle merge of subnodes properly #691)
• test enhancements
• added missing JavaDocs
• renamed all source.xml to template.xml to avoid confusion
• renamed local variables to be consistent (template vs. update vs. setup, result vs. target, workspace vs. target vs. update)

Open tasks:

• CHANGELOG needs to be added
• we could add more robustness: I had situations where I ended up with an empty XML file in my workspace. The could then not be parsed on the next run and was stuck until manual repair. An empty workspace file should be treated as if it did not exist. Also we could discuss how to deal with corrupted XML files that cannot be parsed. However, the good news is that we (or better saying @salimbouch) already have done a lot: There is robustness so a file causing an error is logged but the process is not blocked but continues. If there have been errors the user gets informed and asked to continue. Also the error logging is very precise including the absolute path of the XML files involved and the XPath within the XML document where the error happened. This is great stuff for analysing the root problem and will help us a lot in support (or prevent us from support requests as the users can help themselves).

[hohwille]

For the record: I did not change any testdata semantically. I just followed convention-over-configuration and prefer consistent usage of lowercase for merge:strategy enum values. We should strictly and consistently align such things both in testdata and especially in ide-settings (PR not yet created). Our users will take us by example. If even we do not systematically align this then we can expect a lot of mess in the projects we later have to support.

[coveralls]

Pull Request Test Coverage Report for Build 12814582559

Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 24 unchanged lines in 2 files lost coverage.
• Overall coverage increased (+0.3%) to 68.152%

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Files with Coverage Reduction	New Missed Lines	%
com/devonfw/tools/ide/merge/xmlmerger/matcher/IdComputer.java	4	79.03%
com/devonfw/tools/ide/merge/xmlmerger/XmlMerger.java	20	78.54%

Totals
Change from base Build 12814567403:	0.3%
Covered Lines:	7021
Relevant Lines:	9932

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💛 - Coveralls

[hohwille]

CHANGELOG needs to be added

[jan-vcapgemini]

LGTM.

[salimbouch]

LGTM