#943: rework combine of text nodes in XML merger

[Paras14]

This PR fixes #943

Implemented changes:

• Fixed XmlMergeStrategy.replaceTextNode so that it no longer restarts its search at the first child of the result element on every call. It now receives the index to start searching from and returns the index to continue from, so the n-th textual child of the template is merged into the n-th textual child of the result.
• Fixed XmlMergeStrategy.combineChildNodes to carry that index across loop iterations instead of calling replaceTextNode with no position information.
• Handled the case where the template has more textual children than the result. The surplus nodes are appended.
• Handled the case where the result has more textual children than the template. The surplus nodes are left untouched.
• The node type is now taken from the template, so merging a CDATA section over a plain text node replaces the node instead of writing CDATA content into a plain text node. Previously the append path preserved the node type but the overwrite path did not.
• The append path now trims the template text, which the overwrite path already did. Please confirm this is wanted, as the previous inconsistency may have been intentional.
• Added test cases combine-text-nodes and combine-text-nodes-mixed.

This only affects elements that have more than one textual child, which is why it went unnoticed. Almost all configuration files handled by the merger use a single text node per element, and that case was and still is merged correctly. Multiple textual children occur when a CDATA section sits next to plain text, for example in formatter or file header templates.

Note that the code referenced in the issue has been moved since the issue was written. It is now in cli/src/main/java/com/devonfw/tools/ide/merge/xml/XmlMergeStrategy.java and the reported behaviour was unchanged by that move.

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Testing instructions

Please add conscise, understandable instructions on how a reviewer can test/verify the functionality of your contribution here:

1. Run the test class com.devonfw.tools.ide.merge.xml.XmlMergerTest from your IDE. The relevant test method is testMerger, which is a parameterized test with one execution per subfolder of cli/src/test/resources/xmlmerger. All 21 executions should pass, 19 of which existed before this PR.
2. Check the two executions named combine-text-nodes and combine-text-nodes-mixed. Each test folder contains template.xml as the merge template, target.xml as the existing workspace file, and result.xml as the expected merge output.
3. To see the previous behaviour, copy the folder cli/src/test/resources/xmlmerger/combine-text-nodes onto a checkout without the change in XmlMergeStrategy.java and run XmlMergerTest again. The combine-text-nodes execution then fails with expected:<...text1<![CDATA[text2]]>text3...> but was:<...text3<![CDATA[text5]]>text6...>.
   The test cases cover the following:

Test folder	Element	Template	Workspace file	Covers
combine-text-nodes	elem1	text, CDATA, text	text, CDATA, text	Equal number of textual children, which is the case reported in the issue
combine-text-nodes	elem2	text, CDATA, text	text	Template has more textual children, surplus is appended
combine-text-nodes	elem3	text	text, CDATA, text	Workspace file has more textual children, surplus is kept
combine-text-nodes	elem4	CDATA	text	Template determines whether the result node is text or CDATA
combine-text-nodes-mixed	elem1	text, element, text	text, element, text	Textual children separated by a child element

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Checklist for this PR

Make sure everything is checked before merging this PR. For further info please also see
our DoD.

• When running mvn clean test locally all tests pass and build is successful
• PR title is of the form #«issue-id»: «brief summary» (e.g. #921: fixed setup.bat and not feature/921 fixed setup.bat). If no issue ID exists, title only.
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  with internal
• You have not changed any dependency in pom.xml files or otherwise if runtime dependencies changed, you have updated our LICENSE.asciidoc
• You have formulated clear instructions on how to test your contribution under "Testing instructions"

[coveralls]

Coverage Report for CI Build 31963392865

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Coverage: 72.922%

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• Patch coverage: No coverable lines changed in this PR.

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Coverage Stats

Relevant Lines:	17555
Covered Lines:	13351
Line Coverage:	76.05%
Relevant Branches:	7761
Covered Branches:	5110
Branch Coverage:	65.84%
Branches in Coverage %:	Yes
Coverage Strength:	3.23 hits per line

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💛 - Coveralls

[krystynaShatkovska]

All tests cases pass. combine-text-nodes-mixed and combine-text-nodes cover what is needed. About trim behavior, it is now consistent. As it overwrite and append path trim. Because of getText() method trim, append path now matches overwrite path. Good work!