Re: [tycho-user] What are baseline repositories good for?

[Jonah Graham <jonah@xxxxxxxxxxxxxxxx>]

I am not as negative as Ed about using it because in my experience the code does not use a superficial view of git alone. The Eclipse CDT project and other  Eclipse projects use it, including AFIAK the Eclipse Platform project. While it does use git history, it actually compares the contents of the class files and other files in the jars*. So for example, if your code inlines a constant that changes in some dependency, the git would show no difference, but the class file will be different and therefore a difference to baseline will be reported.

One of the most useful effects of the reproducible build qualifiers is that it prevents a project from releasing the same jar with only build qualifier being different. 

* for the curious, the code that does the comparison is https://git.eclipse.org/c/tycho/org.eclipse.tycho.git/tree/tycho-artifactcomparator/src/main/java/org/eclipse/tycho/zipcomparator/internal which use these interfaces https://git.eclipse.org/c/tycho/org.eclipse.tycho.git/tree/tycho-artifactcomparator/src/main/java/org/eclipse/tycho/artifactcomparator

HTH, 

Jonah 

On Mon., Feb. 17, 2020, 15:01 Ed Willink, <ed@xxxxxxxxxxxxx> wrote:

Hi

On a good day, the reproducible qualifiers avoid you churning a new set of unchanged artefacts every build, thereby saving on distribution bandwidth.

However that good day is totally depend on the fairies, since an unsound superficial view of GIT dependencies rather than a true has-it-changed-test is used.

Do not use.

Regards

Ed Willink

On 17/02/2020 19:21, Felix Dorner wrote:

Hi, 

on the wiki page: 

https://wiki.eclipse.org/Tycho/Reproducible_Version_Qualifiers#What_does_this_actually_do.3F 

I follow along with the jgit based timestamps, but I dont understand what the baseline repository configuration does. The wiki page sais:

The end result is that build output contains new versions of the artifacts that did change and baseline version of the artifacts that did not.

And "change" meaning version, id and "content". How is "content" defined here?

I will have follow up questions :)

Thanks,

Felix

--

Linux. The choice of a GNU generation.

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