Merging semi-parallel universes into one coherent repository

Hello

I created a post on SO about this; pasting it here for convenience:

= = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = http://stackoverflow.com/questions/25193518/fixing-branches-disconnected-from-master

After "completing" a repository migration, we noticed that all of our branches are all behind and ahead of master by hundreds to thousands of commits.

Some context -- originally I used git-svn to migrate the repositories from SVN to git. Later down the line I used this solution to merge multiple (7) repositories into one.

However, I also improvised on that solution for the repositories' branches. The result was disconnected branches -- branches that have all of the commits and proper change history, but are not actually associated with master in any way since the commits in the branches have different SHA's from those in the new, shared master.

Additionally, the original "branching" in the separate repositories happened at different revisions, for example project X might have branched for release 1.0 at revision 30 whereas project Y might have branched fro release 1.0 at revision 42... and all of them have different times (and perhaps multiple times) where they merged back to master.

Is there any clean way to fix this link to make it look like all of these repositories branched together? And to fix the commits so they actually properly map to commits in master? = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = =

I am sure there is a better way to word the above... but basically I have seven used-to-be-separate repositories with the same branches (say r1.0 as above). After some magic with filter-branch, they are all one repository -- all history in-tact. Additionally, same-named branches had their histories mashed together. That's all peachy.

What's *not* peachy is that each of these branches shares commits with master and doesn't know it. Thus each branch looks "disconnected" from master, e.g. there is no pretty branch graph when you look through the history with "git log --pretty=format:"%h %s" --graph".

Does anybody know of a way to rectify this issue?

Let me know if any clarifications are needed.  Help is much appreciated...

-- Ryan