I found myself in the same issue as you, and found out that there is no standard way to do this. However, looking around I found out about a strategy to help do this, and I created a power shell script based on that. I can't remember the source, or I would give them credit. I would explain it, but I its easier to just see the script and the comments.
You could use this script, or if not using windows/powershell, make on based on it. The good thing is that once you have your individual git repos for each submodule, if something fails, its really fast/easy to just delete the new "master" git repo, make changes to the script and just run it again, since its all local.
Beware that there are some cases that are not handled, like having when a sub module has folder that is called the same as another sub module (so if you have a sub module called BIN and then your other sub modules have sub a BIN sub folder, it will fail). Also be sure that all of your sub Modules git repos are up to date before you begin!
You can check out the script in this gist:
Gist Script
if for some reason the gist is down, I've also added it here (albeit a lot less readable)
$GitReposLocation = "path\to\individual\git\repos"; #1 git repo for each module (you svn cloned each one using std layout)
$MasterGitRepoLocation = "path\to\masterRepo"; #the path where you want your main repo that contains all the modules
git reset --hard;
write-host Creating folder $MasterGitRepoLocation -foregroundcolor "green";
mkdir $MasterGitRepoLocation;
write-host Moving to folder $MasterGitRepoLocation -foregroundcolor "green";
cd $MasterGitRepoLocation;
write-host Creating Git Repository -foregroundcolor "cyan";
git init;
#this is hacky, but we need to have an initial commit
"" > root;
git add root;
write-host Creating root node -foregroundcolor "cyan";
git commit -m "Initial commit to create parent root.";
#we are going to be moving files around, and don't want to move the files we already got in our MasterRepo root/workspace
$NotMoveThesFiles = @();
dir |%{$NotMoveThesFiles+=@($_.FullName) };
$repos = @();
# you should add a repo here if for some reasong you don't want to process that one.
# $repos+=@("SomeRepo");
dir -Path $GitReposLocation -Directory |Where-object{ $repos -NotContains $_.Name }|%{$repos+=@($_.Name) };
# for-each repo....
$repos|%{
$SubRepoName = $_;
write-host Processing GitRepo $SubRepoName -foregroundcolor "green";
$Remote = "remote"+$SubRepoName;
#add this git repo (of a module) as a remote of our main repo
write-host Adding reference to $SubRepoName as remote repo -foregroundcolor "cyan";
git remote add -f $Remote $GitReposLocation\$SubRepoName;
#Merge that sub repo into the main repo. The only problem? It will copy that repo's workspace
#directly into our main repo Root folder
write-host Merging remote$SubRepoName/master into master -foregroundcolor "cyan";
git merge remote$SubRepoName/master;
#so now we are going to create a folder with the name of this module (subRepo)
#and move everything that is in the Master's root folder to that folder, except of course
#things that we already had in the root folder before the merge. (in the NotMoveTheseFiles array)
write-host Moving files got from $SubRepoName to a subdir called $SubRepoName -foregroundcolor "green";
#create folder folr the module
mkdir $SubRepoName;
#add these new folde to the list of things we don't want to move into it.
$NotMoveThesFiles+=@($SubRepoName);
#copy all files not in the NotMoveTheseFiles array into the newly created folder.
dir |where-object {$NotMoveThesFiles -NotContains $_} |%{git mv $_ $SubRepoName};
#commit the change where we moved all these files around.
$CommitMessage = "Moving files got from " + $SubRepoName + " to a subdir called $SubRepoName"
git commit -m $CommitMessage;
}
