build: add comparison of MEI versions

[musicEnfanthen]

This PR adds an Ant target to run the MEI version comparison from build.xml. This prepares to include the comparison in the CI build process and gives the ability to include the comparison output file with releases and commits (for the dev branch).
By default, the target compares the current version (dev) to the previous version (MEI 4.0.1), but any other version can be compared via customized inputs.

New ant target tested locally and with docker.

Closes #1256

[bwbohl]

many thanks @musicEnfanthen, this looks all good but maybe we should accompany this with adding the compiled source to https://github.com/music-encoding/schema/tree/main/4.0.1?

[musicEnfanthen]

Yes, agree, at least the canonicalized source for 4.0.1 that is needed for the comparison. I also created "semi-manually" a canonicalized source for v3 (at least it gives the same results as the comparison that is online for v3 vs. v4)

[musicEnfanthen]

Accompanying PR on schema repo is available: music-encoding/schema#7

[bwbohl]

@musicEnfanthen could you resolve the tiny conflict, please?

[musicEnfanthen]

@bwbohl Done, thanks for the pointer.

[bwbohl]

Generally, it works great if the source-files are in place. But I wonder whether the $old.default should probably be fetched to temp or build instead of next to compariosn.xsl?
Moreover, we could think about moving the output to the dist.folder if one runs dist. Which makes me wonder why not by default put the build result of the taret in the build folder?

[musicEnfanthen]

Moreover, we could think about moving the output to the dist.folder if one runs dist. Which makes me wonder why not by default put the build result of the taret in the build folder?

The comparions.html needs to be in the same folder as the resources folder to be displayed correctly (with css and js). That's the only reason why I moved the output file next to the XSLT.

[musicEnfanthen]

Thanks for the additional improvements @bwbohl . Looks great.

Reworked your suggestions for the ant target. As sugested, it now defines the location of the default old file in the build folder (since we run canonicalize-source beforehand the build folder will be created in any case and can be used). If it does not find a file there, it will download it from the schema repo. It will fail early now when the old source file cannot be found (which is probably only possible if there is a custom user input since downloaded default file should be available). So the checks if the file is available can be skipped with later steps. I left the output folder in the utils/compare_versions directory since the html file will need the resources to be displayed correctly. We can improve and move that in the future, but would keep it for now.

In the XSLT, I refactored the version variables and guideline links so that it works now with dev and major versions.

[bwbohl]

with the two mentioned changes it works fine locally.

[musicEnfanthen]

Unfortunately, your suggestions will not work on Win. The XSLT does not find the old.file then.

[bwbohl]

In the current state, it does not work on macOS, though…