Debugging git push/clone issues with ip6

Problem: You're doing "git push" or "git clone" and it takes forever to connect.

This could be a lot of things. In my case it was a firewall issue on a dual stack server hosting my repository.

How can you tell?

git config -global core.sshCommand "ssh -vvv"

This enabled verbose mode for SSH. Now try to clone your repo and you'll get a lot more information.

In my case, it was a DNS resolution problem.

[email protected]:test $ git pull origin master
OpenSSH_7.4p1, LibreSSL 2.5.0
debug1: Reading configuration data /Users/dkilgo/.ssh/config
debug1: Reading configuration data /etc/ssh/ssh_config
debug2: resolving "" port 49001
debug2: ssh_connect_direct: needpriv 0
debug1: Connecting to [xxxx:xx:xxxx:x:xxx:xx:xx:xxx] port 49001.
debug1: connect to address xxxx:xx:xxxx:x:xxxx:xx:xx:xxx port 49001: Operation timed out
debug1: Connecting to [] port 49001.
debug1: Connection established.

I got a timeout on the ip6 address. The SSH port on this dual-stack server is being blocked. Once it fails, git will try ip4 which works.

Since I don't have control over the network here, I can work around this issue with ssh's config.

How do I fix this without breaking everything else that uses ip6?

You could just disable ip6 in your network settings. In 2017, that's not the most practical solution. We can do that for just one host in our SSH settings and get the same effect.

Edit your ~/.ssh/conf and add

AddressFamily inet

This tells ssh to only use ip4 for this host. This makes my one buggy host happy and doesn't mess with the rest of the internet. If you discover ip4 is the problem for you and ip6 works, set that to "inet6" instead. 

Don't forget to turn off that verbose logging we turned on earlier.

git config -global core.sshCommand "ssh"


If this didn't fix your issue, try git's debug options.

GIT_CURL_VERBOSE=1 GIT_TRACE=1 git pull origin master

The GIT_TRACE environment var makes git output more debug info during any operation. Setting it like this means it will only impact this command.

If you want this to work for any user or app, you can export that var.


and any call to git will output debug info, even from a tool like source tree or git embeded in an IDE. More info on git environment variables.

Steps to migrate a code repository from CVS to GIT

CVS has served us well for many years. The interface in eclipse is so good it was really hard to justify switching to something else. 

That day has come. This tutorial was done on a mac from the command line interface. GIT comes with mac os now and cvs2git was avalible via the brew install system.
This process should also work on linux command line too.


  • A linux/Unix computer.
  • Install git
  • Install cvs2svn
  • Direct access to CVS repository files.

Step 1: Make a copy of your raw CVS repository.
This doesn't work correctly with a working copy.
For this example its on my desktop.


Step 2: Let csv2git to process the repository.

cvs2git –blobfile="~/Desktop/blob.dat" –dumpfile="~/Desktop/dump.dat" –username="dkilgo" ~/Desktop/cvs-local/my-sample-project

If your cvs repository is corrupt, you may recieve warnings from cvs2git like the following:

ERROR: A CVS repository cannot contain both ~/Desktop/cvs-local/my-sample-project/help/internal/compile/Release_text0.htm,v and ~/Desktop/cvs-local/my-sample-project/help/internal/compile/Attic/Release_text0.htm,v
ERROR: A CVS repository cannot contain both ~/Desktop/cvs-local/my-sample-project/help/internal/compile/Release_text1.htm,v and ~/Desktop/cvs-local/my-sample-project/help/internal/compile/Attic/Release_text1.htm,v

In CVS when a file is deleted, it moves into the attic folder. Its not techniclly correct for both files to exist. You'll have to examine both files with a text editor and see which one has the highest revision number and delete the older file.
All the times I encountered this error, the Attic version was older.
Once you've resolved all the errors, re-run the cvs2git command.

A successful run will provide something like the following output:

Time for pass1 (CollectRevsPass): 5.119 seconds.
—– pass 2 (CleanMetadataPass) —–
Converting metadata to UTF8…
Time for pass2 (CleanMetadataPass): 0.026 seconds.
—– pass 3 (CollateSymbolsPass) —–
Checking for forced tags with commits…
Time for pass3 (CollateSymbolsPass): 0.011 seconds.
—– pass 4 (FilterSymbolsPass) —–
Filtering out excluded symbols and summarizing items…
Time for pass4 (FilterSymbolsPass): 74.65 seconds.
—– pass 5 (SortRevisionsPass) —–
Sorting CVS revision summaries…
Time for pass5 (SortRevisionsPass): 0.179 seconds.
—– pass 6 (SortSymbolsPass) —–
Sorting CVS symbol summaries…
Time for pass6 (SortSymbolsPass): 0.110 seconds.
—– pass 7 (InitializeChangesetsPass) —–
Creating preliminary commit sets…
Time for pass7 (InitializeChangesetsPass): 1.975 seconds.
—– pass 8 (BreakRevisionChangesetCyclesPass) —–
Breaking revision changeset dependency cycles…
Time for pass8 (BreakRevisionChangesetCyclesPass): 0.727 seconds.
—– pass 9 (RevisionTopologicalSortPass) —–
Generating CVSRevisions in commit order…
Time for pass9 (RevisionTopologicalSortPass): 0.547 seconds.
—– pass 10 (BreakSymbolChangesetCyclesPass) —–
Breaking symbol changeset dependency cycles…
Time for pass10 (BreakSymbolChangesetCyclesPass): 1.134 seconds.
—– pass 11 (BreakAllChangesetCyclesPass) —–
Breaking CVSSymbol dependency loops…
Time for pass11 (BreakAllChangesetCyclesPass): 1.681 seconds.
—– pass 12 (TopologicalSortPass) —–
Generating CVSRevisions in commit order…
Time for pass12 (TopologicalSortPass): 1.520 seconds.
—– pass 13 (CreateRevsPass) —–
Mapping CVS revisions to Subversion commits…
Creating Subversion r1 (Project initialization)
Creating Subversion r2 (commit)
Creating Subversion r3 (commit)
Creating Subversion r4 (commit)

Time for pass13 (CreateRevsPass): 1.538 seconds.
—– pass 14 (SortSymbolOpeningsClosingsPass) —–
Sorting symbolic name source revisions…
Time for pass14 (SortSymbolOpeningsClosingsPass): 0.854 seconds.
—– pass 15 (IndexSymbolsPass) —–
Determining offsets for all symbolic names…
Time for pass15 (IndexSymbolsPass): 0.373 seconds.
—– pass 16 (OutputPass) —–
Time for pass16 (OutputPass): 1.455 seconds.

cvs2svn Statistics:
Total CVS Files:              1417
Total CVS Revisions:          2982
Total CVS Branches:           1482
Total CVS Tags:              36376
Total Unique Tags:              59
Total Unique Branches:           2
CVS Repos Size in KB:        25792
Total SVN Commits:             579
First Revision Date:    Thu May 17 08:25:14 2007
Last Revision Date:     Fri Aug 17 11:13:14 2013
Timings (seconds):
 5.12   pass1    CollectRevsPass
 0.03   pass2    CleanMetadataPass
 0.01   pass3    CollateSymbolsPass
74.65   pass4    FilterSymbolsPass
 0.18   pass5    SortRevisionsPass
 0.11   pass6    SortSymbolsPass
 1.97   pass7    InitializeChangesetsPass
 0.73   pass8    BreakRevisionChangesetCyclesPass
 0.55   pass9    RevisionTopologicalSortPass
 1.13   pass10   BreakSymbolChangesetCyclesPass
 1.68   pass11   BreakAllChangesetCyclesPass
 1.52   pass12   TopologicalSortPass
 1.54   pass13   CreateRevsPass
 0.85   pass14   SortSymbolOpeningsClosingsPass
 0.37   pass15   IndexSymbolsPass
 1.46   pass16   OutputPass
91.90   total

Step 3: Create a git repository and import the data into it.

mkdir sample-git
cd sample-git
git init
cat ../blob.dat ../dump.dat | git fast-import

Which will create the following output:

git-fast-import statistics:
Alloc'd objects:       5000
Total objects:         3057 (      1285 duplicates                  )
      blobs  :         1754 (      1270 duplicates       1254 deltas of       1668 attempts)
      trees  :          956 (        15 duplicates        758 deltas of        892 attempts)
      commits:          347 (         0 duplicates          0 deltas of          0 attempts)
      tags   :            0 (         0 duplicates          0 deltas of          0 attempts)
Total branches:          44 (         6 loads     )
      marks:     1073741824 (      3371 unique    )
      atoms:            997
Memory total:          2594 KiB
       pools:          2360 KiB
     objects:           234 KiB
pack_report: getpagesize()            =       4096
pack_report: core.packedGitWindowSize = 1073741824
pack_report: core.packedGitLimit      = 8589934592
pack_report: pack_used_ctr            =        802
pack_report: pack_mmap_calls          =         41
pack_report: pack_open_windows        =          1 /          1
pack_report: pack_mapped              =   31753114 /   31753114

Have a look in the git repo directory and you'll find its empy. Where's all your stuff?
Its in the .git directory. You don't have a working copy checked out yet.

Do "git checkout" to get a working copy of your repo.

Now you have a functional git repository with all your CVS comments, tags and branches.

Side note:

Changing to git ment updating our deployment scripts as well.
The old way with CVS looked like this:

cvs -d /home/cvs/devel -q export -r $tag -d $stageDir/sample-project smaple-project

Git has a little more overhead in that by default the cloned repo contains all the branches and commits, not just the tagged/current version.
That means what it checks out is usually a bit bigger than what would be picked up by the CVS export.
To workaround that, you can set the –depth param to limit git where it only cares about the last version of each file and folder.

/usr/local/bin/git clone –depth 1 –branch $tag git\ $stageDir/sample-project/

I always remove the revision control files before deployment. Its a pain with CVS and SVN. With git, its a snap because they're all in the same folder.

rm -f -r $stageDir/sample-project/.git