How can I debug git/git-shell related problems?

Question

How can I have some debug information regarding git/git-shell?

I had a problem, that user1 could clone a repository without problem, while user2<

Answer 1

If its over SSH, you can use the following:

For a higher debug level for type -vv or -vvv for debug level 2 and 3 respectively:

# Debug level 1
GIT_SSH_COMMAND="ssh -v" git clone <repositoryurl>

# Debug level 2
GIT_SSH_COMMAND="ssh -vv" git clone <repositoryurl>

# Debug level 3
GIT_SSH_COMMAND="ssh -vvv" git clone <repositoryurl>

This is mainly useful to handle public and private key problems with the server. You can use this command for any git command, not only 'git clone'.

Answer 2

Debugging

Git has a fairly complete set of traces embedded which you can use to debug your git problems.

To turn them on, you can define the following variables:

• GIT_TRACE for general traces,
• GIT_TRACE_PACK_ACCESS for tracing of packfile access,
• GIT_TRACE_PACKET for packet-level tracing for network operations,
• GIT_TRACE_PERFORMANCE for logging the performance data,
• GIT_TRACE_SETUP for information about discovering the repository and environment it’s interacting with,
• GIT_MERGE_VERBOSITY for debugging recursive merge strategy (values: 0-5),
• GIT_CURL_VERBOSE for logging all curl messages (equivalent to curl -v),
• GIT_TRACE_SHALLOW for debugging fetching/cloning of shallow repositories.

Possible values can include:

• true, 1 or 2 to write to stderr,
• an absolute path starting with / to trace output to the specified file.

For more details, see: Git Internals - Environment Variables

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SSH

For SSH issues, try the following commands:

echo 'ssh -vvv "$*"' > ssh && chmod +x ssh
GIT_SSH="$PWD/ssh" git pull origin master

or use ssh to validate your credentials, e.g.

ssh -vvvT git@github.com

or over HTTPS port:

ssh -vvvT -p 443 git@ssh.github.com

^{Note: Reduce number of -v to reduce the verbosity level.}

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Examples

$ GIT_TRACE=1 git status
20:11:39.565701 git.c:350               trace: built-in: git 'status'

$ GIT_TRACE_PERFORMANCE=$PWD/gc.log git gc
Counting objects: 143760, done.
...
$ head gc.log 
20:12:37.214410 trace.c:420             performance: 0.090286000 s: git command: 'git' 'pack-refs' '--all' '--prune'
20:12:37.378101 trace.c:420             performance: 0.156971000 s: git command: 'git' 'reflog' 'expire' '--all'
...

$ GIT_TRACE_PACKET=true git pull origin master
20:16:53.062183 pkt-line.c:80           packet:        fetch< 93eb028c6b2f8b1d694d1173a4ddf32b48e371ce HEAD\0multi_ack thin-pack side-band side-band-64k ofs-delta shallow no-progress include-tag multi_ack_detailed symref=HEAD:refs/heads/master agent=git/2:2.6.5~update-ref-initial-update-1494-g76b680d
...