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https://issues.apache.org/jira/browse/LUCENE-6933?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Dawid Weiss updated LUCENE-6933:
--------------------------------
    Description: 
Goals:
* selectively drop projects and core-irrelevant stuff:
  ** {{lucene/site}}
  ** {{lucene/nutch}}
  ** {{lucene/lucy}}
  ** {{lucene/tika}}
  ** {{lucene/hadoop}}
  ** {{lucene/mahout}}
  ** {{lucene/pylucene}}
  ** {{lucene/lucene.net}}
  ** {{lucene/old_versioned_docs}}
  ** {{lucene/openrelevance}}
  ** {{lucene/board-reports}}
  ** {{lucene/java/site}}
  ** {{lucene/java/nightly}}
  ** {{lucene/dev/nightly}}
  ** {{lucene/dev/lucene2878}}
  ** {{lucene/sandbox/luke}}
  ** {{lucene/solr/nightly}}
* preserve the history of all changes to core sources (Solr and Lucene).
  ** {{lucene/java}}
  ** {{lucene/solr}}
  ** {{lucene/dev/trunk}}
  ** {{lucene/dev/branches/branch_3x}}
  ** {{lucene/dev/branches/branch_4x}}
  ** {{lucene/dev/branches/branch_5x}}
* provide a way to link git commits and history with svn revisions (amend the 
log message).
* annotate release tags
* deal with large binary blobs (JARs): keep empty files instead for their 
historical reference only.

Non goals:
* no need to preserve "exact" merge history from SVN (see "impossible" below).
* Ability to build ancient versions is not an issue.

Impossible:
* It is not possible to preserve SVN "merge history" because of the following 
reasons:
  ** Each commit in SVN operates on individual files. So one commit can "copy" 
(and record a merge) files from anywhere in the object tree, even modifying 
them along the way. There simply is no equivalent for this in git. 
  ** There are historical commits in SVN that apply changes to multiple 
branches in one commit ({{r1569975}}).
* Because exact merge tracking is impossible then what follows is that exact 
"linearized" history of a given file is also impossible to record. Let's say 
changes X, Y and Z have been applied to a branch of a file A and then merged 
back. In git, this would be reflected as a single commit flattening X, Y and Z 
(on the target branch) and three independent commits on the branch. The 
"copy-from" link from one branch to another cannot be represented because, as 
mentioned, merges are done on entire branches in git, not on individual files. 
Yes, there are commits in SVN history that have selective file merges (not 
entire branches).


  was:
Goals:
- selectively drop unnecessary stuff from history (cms/, javadocs/, JARs and 
perhaps other binaries),
- *preserve* history of all core sources. So svn log IndexWriter has to go back 
all the way back to when Doug was young and pretty. Ooops, he's still pretty of 
course.
- provide a way to link git history with svn revisions. I would, ideally, 
include a "imported from svn:rev XXX" in the commit log message.
- annotate release tags and branches. I don't care much about interim branches 
-- they are not important to me (please speak up if you think otherwise).

Non goals
- no need to preserve "exact" history from SVN (the project may skip JARs, 
etc.). Ability to build ancient versions is not an issue.


> Create a (cleaned up) SVN history in git
> ----------------------------------------
>
>                 Key: LUCENE-6933
>                 URL: https://issues.apache.org/jira/browse/LUCENE-6933
>             Project: Lucene - Core
>          Issue Type: Task
>            Reporter: Dawid Weiss
>            Assignee: Dawid Weiss
>
> Goals:
> * selectively drop projects and core-irrelevant stuff:
>   ** {{lucene/site}}
>   ** {{lucene/nutch}}
>   ** {{lucene/lucy}}
>   ** {{lucene/tika}}
>   ** {{lucene/hadoop}}
>   ** {{lucene/mahout}}
>   ** {{lucene/pylucene}}
>   ** {{lucene/lucene.net}}
>   ** {{lucene/old_versioned_docs}}
>   ** {{lucene/openrelevance}}
>   ** {{lucene/board-reports}}
>   ** {{lucene/java/site}}
>   ** {{lucene/java/nightly}}
>   ** {{lucene/dev/nightly}}
>   ** {{lucene/dev/lucene2878}}
>   ** {{lucene/sandbox/luke}}
>   ** {{lucene/solr/nightly}}
> * preserve the history of all changes to core sources (Solr and Lucene).
>   ** {{lucene/java}}
>   ** {{lucene/solr}}
>   ** {{lucene/dev/trunk}}
>   ** {{lucene/dev/branches/branch_3x}}
>   ** {{lucene/dev/branches/branch_4x}}
>   ** {{lucene/dev/branches/branch_5x}}
> * provide a way to link git commits and history with svn revisions (amend the 
> log message).
> * annotate release tags
> * deal with large binary blobs (JARs): keep empty files instead for their 
> historical reference only.
> Non goals:
> * no need to preserve "exact" merge history from SVN (see "impossible" below).
> * Ability to build ancient versions is not an issue.
> Impossible:
> * It is not possible to preserve SVN "merge history" because of the following 
> reasons:
>   ** Each commit in SVN operates on individual files. So one commit can 
> "copy" (and record a merge) files from anywhere in the object tree, even 
> modifying them along the way. There simply is no equivalent for this in git. 
>   ** There are historical commits in SVN that apply changes to multiple 
> branches in one commit ({{r1569975}}).
> * Because exact merge tracking is impossible then what follows is that exact 
> "linearized" history of a given file is also impossible to record. Let's say 
> changes X, Y and Z have been applied to a branch of a file A and then merged 
> back. In git, this would be reflected as a single commit flattening X, Y and 
> Z (on the target branch) and three independent commits on the branch. The 
> "copy-from" link from one branch to another cannot be represented because, as 
> mentioned, merges are done on entire branches in git, not on individual 
> files. Yes, there are commits in SVN history that have selective file merges 
> (not entire branches).



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