git Notes

Chances are that you may need to know some git when using fastai - for example if you want to contribute to the project, or you want to undo some change in your code tree. This document has a variety of useful recipes that might be of help in your work.

How to Make a Pull Request (PR)

While this guide is mostly suitable for creating PRs for any github project, it includes several steps specific to the fastai project repositories, which currently are:

If you already know how to make PRs, you only need to read: the “Step 3” and “Step 5” sections, since they are unique requirements for the fastai project.

The following instructions use USERNAME as a github username placeholder. The easiest way to follow this guide is to copy-n-paste the whole section into a file, replace USERNAME with your real username and then follow the steps.

All the examples in this guide are written for working with the fastai1 repository. If you’d like to contribute to other fastai-project repositories, just replace fastai with that other repository name in the instructions below.

For the purpose of these examples, we will clone into a folder fastai-fork, to differentiate from fastai which you most likely already checked out to install it.

Also don’t get confused between the fastai github username, the fastai repository, and the fastai module directory, where the python code resides. The following url shows all three, in the order they have been mentioned:

https://github.com/fastai/fastai1/tree/master/fastai
                     |       |                  |
                 username reponame        modulename

Below you will find detailed steps towards creating a PR.

Helper Program

There is a smart program that can do all the heavy lifting of the first 2 steps for you. Then you just need to do your work, commit changes and submit PR. To run it:

curl -O https://raw.githubusercontent.com/fastai/git-tools/master/fastai-make-pr-branch
chmod a+x fastai-make-pr-branch
./fastai-make-pr-branch https your-github-username fastai new-feature

For more details run:

./fastai-make-pr-branch

While this is new and experimental, you probably want to place that script somewhere in your $PATH, so that you could invoke it from anywhere. Once it is well tested, it’ll probably get installed automatically with the fastai package.

And now we also have a python version of the same:

curl -O https://raw.githubusercontent.com/fastai/git-tools/master/fastai-make-pr-branch-py
chmod a+x fastai-make-pr-branch-py
./fastai-make-pr-branch-py https your-github-username fastai new-feature

Step 1. Start With a Synced Fork Checkout

1a. First time

If you made the fork of the desired repository already, proceed to section 1b.

If it’s your first time, you just need to make a fork of the original repository:

Go to https://github.com/fastai/fastai1 and in the right upper corner click on [Fork]. This will generate a fork of this repository, and you will be redirected to github.com/USERNAME/fastai.

Clone the main repository fork. Click on [Clone or download] button to get the clone url and then clone your repository.

Choose the SSH option if you have SSH configured with github and run:

git clone [email protected]:USERNAME/fastai.git fastai-fork

otherwise choose the HTTPS option:

git clone https://github.com/USERNAME/fastai.git fastai-fork

Make sure the url has your username in it. If the username is fastai you’re cloning the original repo and not your fork. This will not do what you need.

Then move into the newly created directory:

cd fastai-fork

and run the setup tool:

tools/run-after-git-clone

for any of the fastai project repositories, except fastprogress where it doesn’t exist.

Finally, let’s setup this fork to track the upstream:

Using SSH:

git remote add upstream [email protected]:fastai/fastai.git

Using HTTPS:

git remote add upstream https://github.com/fastai/fastai1.git

You can check your setup:

git remote -v

It should show:

If you used SSH:

origin  [email protected]:USERNAME/fastai.git (fetch)
origin  [email protected]:USERNAME/fastai.git (push)
upstream  [email protected]:fastai/fastai.git (fetch)
upstream  [email protected]:fastai/fastai.git (push)

If you used HTTPS:

origin  https://github.com/USERNAME/fastai.git (fetch)
origin  https://github.com/USERNAME/fastai.git (push)
upstream  https://github.com/fastai/fastai1.git (fetch)
upstream  https://github.com/fastai/fastai1.git (push)

You can now proceed to step 2.

1b. Subsequent times

If you make a PR right after you made a fork of the original repository, the two repositories are aligned and you can easily create a PR. If time passes the original repository starts diverging from your fork, so when you work on your PRs you need to keep your master fork in sync with the original repository.

You can tell the state of your fork, by going to https://github.com/USERNAME/fastai and seeing something like:

This branch is 331 commits behind fastai:master.

So, let’s synchronize the two:

Place yourself in the master branch of the forked repository:
- Either you go back to a repository you checked out earlier and switch to the master branch:
```
cd fastai-fork
git checkout master
```
- or you make a new clone
```
git clone git://github.com/USERNAME/fastai.git fastai-fork
cd fastai-fork
git remote add upstream [email protected]:fastai/fastai.git
```
and set things up as before (except for the fastprogress repository):
```
tools/run-after-git-clone
```
Use the https version https://github.com/USERNAME/fastai if you don’t have ssh configured with github.
Sync the forked repository with the original repository:
```
git fetch upstream
git checkout master
git merge --no-edit upstream/master
git push
```
Now you can branch off this synced master branch.

Validate that your fork is in sync with the original repository by going to https://github.com/USERNAME/fastai and checking that it says:
```
This branch is even with fastai:master.
```
Now you can work on a new PR.

Step 2. Create a Branch

It’s very important that you always work inside a branch. If you make any commits into the master branch, you will not be able to make more than one PR at the same time, and you will not be able to synchronize your forked master branch with the original without doing a reset. If you made a mistake and committed to the master branch, it’s not the end of the world, it’s just that you made your life more complicated. This guide will explain how to deal with this situation.

Create a branch with any name you want, for example new-feature-branch, and switch to it. Then set this branch’s upstream, so that you could do git push and other git commands without needing to pass any more arguments.
```
git checkout -b new-feature-branch
git push --set-upstream origin new-feature-branch
```

Step 3. Prepare Your Checkout

Uninstall preinstalled fastai

In order for you to be able to test your code against this particular fastai checkout, first make sure to uninstall the released version of fastai that you may have already installed.
```
conda uninstall -y fastai
```
If you previously installed fastai via pip you don’t need to uninstall it - pip will automatically do it for you when you install fastai in the next step.

Also this is probably a good time for you to deepen your understanding of Editable installs.
Install the prerequisites.

No matter which repository you contribute to, unless you have already done so install the developer prerequisites:

Use an existing checkout, or make one:
```
git clone https://github.com/fastai/fastai1 fastai-fork
cd fastai-fork
```
and make an editable install with the developer prerequisites:
```
pip install -e ".[dev]"
```
Now configure the nbstripout filters if you haven’t yet done so (the helper script does it automatically for you if you have used it to create the PR branch).

Move into the root of the repository where your PR branch is and run:
```
tools/run-after-git-clone # or python tools\run-after-git-clone on windows
```

Step 4. Write Your Code

This is where the magic happens.

Create new code, fix bugs, add/correct documentation.

Step 5. Test Your Changes

Test that your changes don’t break things. Choose one according to which project you are creating PR for:

fastai

In the fastai repository, if you made changes to the libraries under fastai or you added/changed anything under tests, move into the root of the repository and run:
```
 make test
```
or if you don’t have make, just:
```
 pytest
```
docs_src

In the docs_src folder, if you made changes to the code cells of the documentation notebooks, run:
```
 cd docs_src
 ./run_tests.sh
```
You will need at least 8GB free GPU RAM to run these tests.

Please ignore this if you’re just adding/changing the prose.

Step 6. Push Your Changes

When you’re happy with the results, commit the new code:
```
git commit -a
```
-a will automatically commit changes to any of the repository files.

If you created new files, first tell git to track them:
```
git add newfile1 newdir2 ...
```
and then commit.
Finally, push the changes into the branch of your fork:
```
git push
```

Step 7. Submit Your PR

Go to github and make a new Pull Request:

Usually, if you go to https://github.com/USERNAME/fastai github will notice that you committed to a new branch and will offer you to make a PR, so you don’t need to figure out how to do it.

If for any reason it’s not working, go to https://github.com/USERNAME/fastai/tree/new-feature-branch (replace new-feature-branch with the real branch name, and click [Pull Request] in the right upper corner.

If you work on several unrelated PRs, make different directories for each one, ideally using the same directory name as the branch name, to simplify things.

Step 8. Passing CI Tests

Once your PR was submitted, you will see on github that we have various tests running on CI servers that will validate your PR. The tests run on various platforms and on both pip and conda virtual environments, so we have all bases covered.

Do note that since our test suite contains many non-deterministic tests, at times you will notice that one of the checks on a single platform will fail. Most of the time it’s normal, and there is nothing to worry about. We are constantly trying to make those less error-prone, but we can’t make them too loose either, otherwise the test would be ineffective. Hence the occasional failures.

You can go to Azure CI following the failing link and check what has failed. Unless you see the failure is related to your PR, please ignore it and consider that all tests have succeeded. The maintainer can always initiate a re-run of a CI job on the failed platform if need be.

How to Keep Your Feature Branch Up-to-date

Normally you don’t need to worry about updating your feature branch to synchronize with the fastai code base (upstream master). The only time you must perform the update is when the same code you have been working on has undergone changes in the master. So when you submit a PR, github will tell you that there is a merge conflict.

You could update your feature branch directly, but it’s best to update the master branch of your fork, first.

Step 1: sync your forked master branch:

 cd my-cool-feature # your fastai fork clone directory
 git fetch upstream
 git checkout master
 git merge --no-edit upstream/master
 git push --set-upstream origin master

Step 2: update your feature branch my-cool-feature:

 git checkout my-cool-feature
 git merge origin/master

Step 3: resolve any conflicts resulting from the merge (using your editor or a special merge tool), followed by git add to the files which had conflict.
Step 4: push to github the updates to your branch:
```
 git push
```
If your PR is already open, github will automatically update its status showing the new commits and the conflict shouldn’t be there any more if you followed the steps above.

How To Reset Your Forked Master Branch

If you haven’t been careful to create a branch, and committed to the master branch of your forked repository, you no longer will be able to sync it with the original repository, without resetting it. And when you will want to create a branch, it’ll have issues during PR, since it will be made against a diverged origin.

Of course, the brute-force approach is to go to github, delete your fork (which will delete any of the work you have done on this fork, including any branches, so be very careful if you decided to do that, since there will be no way to recover your data).

A much safer approach is to reset the HEAD of your forked master with the HEAD of the original repository:

If you haven’t setup up the upstream, do it now:

   git remote add upstream [email protected]:fastai/REPONAME.git

and then do the reset:

   git fetch upstream
   git update-ref refs/heads/master refs/remotes/upstream/master
   git checkout master
   git stash
   git reset --hard upstream/master
   git push origin master --force

Where am I?

Now that you have the original repository, the forked repository and its branches how do you know which of the repository and the branch you are currently in?

Which repository am I in?

 git config --get remote.origin.url | sed 's|^.*//||; s/.*@//; s/[^:/]\+[:/]//; s/.git$//'

e.g.: stas00/fastai

Which branch am I on?
```
 git branch | sed -n '/\* /s///p'
```
e.g.: new-feature-branch7

Combined:

 echo $(git config --get remote.origin.url | sed 's|^.*//||; s/.*@//; s/[^:/]\+[:/]//; s/.git$//')/$(git branch | sed -n '/\* /s///p')

e.g.: stas00/fastai/new-feature-branch7

But that’s not a very efficient process to constantly ask the system to tell you where you are. Why not make it automatic and integrate this into your bash prompt (assuming that use bash).

bash-git-prompt

Enter bash-git-prompt, which not only tells you which virtual environment you are in and which username, repo, branch you’re on, but it also provides very useful visual indications on the state of your git checkout - how many files have changed, how many commits are waiting to be pushed, whether there are any upstream changes, and much more.

I currently work on 4 different fastai project repositories and 4 corresponding forks, and several branches in all of them, so I was very lost until I started using this tool. To give you a visual of various prompts I have as of this writing:

   (pytorch-dev) /fastai/ci-experiments [fastai/fastai:ci-experiments|·6]>

   (pytorch-dev) /fastai/linkcheck [fastai/fastai:master]>

   (pytorch-dev) /stas00/fork [stas00/fastai:master|·3]>

   (pytorch-dev) /fastai/wip [fastai/fastai:master|+2?10·3]>

The numbers after the branch are modified/untracked/stashed counts. The leading (pytorch-dev) is the currently activated conda env name.

If you’re not using bash or fish shell, search for forks of this idea for other shells.

hub

hub == hub helps you win at git

hub is the command line GitHub. It provides integration between git and github in command line. One of the most useful commands is creating pull request by just typing hub pull-request in your terminal.

We have a script that will do the installing for you: hub-install.py.

If for any reason you can’t use the script, here are the manual installation instructions:

There is a variety of ways to install this application (written in go), but the easiest is to download the latest binary for your platform at https://github.com/github/hub/releases/latest, un-archiving the package and running ./install, for example for the linux-64 build:

wget https://github.com/github/hub/releases/download/v2.5.1/hub-linux-amd64-2.5.1.tgz
tar -xvzf hub-linux-amd64-2.5.1.tgz
cd hub-linux-amd64-2.5.1
sudo ./install

You can add a prefix to install it to a different location, for example, under your home:

prefix=~ ./install

or say you wanted to install it inside your active conda environment:

prefix=`which conda | sed 's/\/bin\/conda//'` ./install

Either of the these two should give you the location of the your active conda environment:

which conda | sed 's/\/bin\/conda//'
conda info | grep 'location' | awk '{print $5}'

but the first one is more reliable, conda info’s output may change down the road.

Github Shortcuts

show commits by author: ?author=github_username

You can filter commits by author in the commit view by appending param ?author=github_username.

For example, the link https://github.com/fastai/fastai1/commits/master?author=jph00 shows a list of commits jph00 commits to the fastai1 repository.
show commits by range: master@{time}..master

You can create a compare view in GitHub by using the URL github.com/user/repo/compare/{range}. Range can be two SHAs like sha1…sha2 or two branch names like master…my-branch. Range is also smart enough to take time into consideration.

For example, you can filter a list of commits since yesterday by using format like master@{1.day.ago}…master. The link https://github.com/fastai/fastai1/compare/master@{1.day.ago}…master, for example, gets all commits since yesterday for the fastai repository:
show .diff & .patch

Add .diff or .patch to the URLs of compare view, pull request or commit page to get the diff or patch in text format.

For example, the link https://github.com/fastai/fastai1/compare/master@{1.day.ago}…master.patch gets the patch for all the commits since yesterday in the fastai repository.
line linking

In any file view, when you click one line or multiple lines by pressing SHIFT, the URL will change to reflect your selections. You can tell others to look at a specific line of code, or a specific chunk of code, using just that link.
delete a fork
1. Go to github.com/USERNAME/FORKED-REPO-NAME/
2. Hit Settings
3. Scroll down and hit [Delete this repository]
replace, USERNAME with your github username, and FORKED-REPO-NAME with the repository name

Revisions

relative refs

^      - one commit at a time (parent of the specified commit)
master^  = the first parent of master
master^^ = the first grandparent of master
~<num> - several commits

Operations

add

git add [folder/file]

remove

git rm [folder/file]

remove remote file copy only. e.g. remove database.yml that is already checked in but leaving the local copy untouched. This is intensively handy for removing ignored files that are already pushed without removing the local copies.

git rm --cached database.yml

status

git status

brief status

git status -s

push

git push

dry-run (do everything except for the actually sending of the data)

git push --dry-run

but it doesn’t show anything useful - see commands below for visual hints of what will happen

show which files have changed and view the diff compared to the remote master branch HEAD

git diff --stat --patch origin master

list of files to be pushed

git diff --stat --cached [remote/branch]

show code diff of the files to be pushed

git diff [remote repo/branch]

show full file paths of the files that will change

git diff --numstat [remote repo/branch]

commit

git commit -a

-a is crucial as w/o it you need to git add every file that has changed!

There is also -A, but careful using it, as it’ll add any tracked files, which is probably not what you want most of the time. Better forget about this option.

authentication

cache auth

git config --global credential.helper cache

adjust caching time

git config --global credential.helper 'cache --timeout=36000'

update

git pull

git pull is shorthand for

git fetch
git merge FETCH_HEAD

display the incoming/outgoing changes before pull/push

git log ^master origin/master
git log master ^origin/master

search/replace

How to safely and efficiently search/replace files in git repo using CLI. The operation must not touch anything under .git/

find . -type d -name ".git" -prune -o -type f -exec perl -pi -e 's|OLDSTR|NEWSTR|g' {} \;

but it touch(1)es all files which slows down git-side

so we want to do it on files that actually contain the old pattern

grep --exclude-dir=.git -lIr "OLDSTR" . | xargs -n1 perl -pi -e 's|OLDSTR|NEWSTR|g'

git GUI

git

git gui

gitk

gitk --all

contributors

show a list of contributors ordered by number of commits. Similar to the contributors view of GitHub.

git shortlog -sn

search git history

to find all commits where commit message contains given word, use

git log --grep=word_to_search_for

to search all of git history for a string

git log -Sword_to_search_for

this will find any commit that added or removed the string password. Here are a few extra options:

-p: will show the diffs. If you provide a file (-p file), it will generate a patch for you.
-G: looks for differences whose added or removed line matches the given regexp, as opposed to
-S, which “looks for differences that introduce or remove an instance of string”.
--all: searches over all branches and tags; alternatively, use --branches[=<pattern>] or --tags[=<pattern>]

search and exclude certain paths from the results:

exclude subfolder foo

git log -- . ":(exclude)foo"

exclude several subfolders

git log -- . ":(exclude)foo" ":(exclude)bar"

exclude specific elements in that subfolder

git log -- . ":(exclude)foo/bar/file"

exclude any given file in that subfolder

git log -- . ":(exclude)foo/*file"
git log -- . ":(exclude,glob)foo/*file"

make exclude case insensitive

git log -- . ":(exclude,icase)FOO"

which branch contains a specified sha key

git branch –contains SHA

cherry picking

choose a commit rev from one branch (e.g. PR) and merge it the current checkout

git show <commit>        # check that this is the right rev
git cherry-pick <commit> # merge it into the current checkout
git push

to merge a range of commits:

git cherry-pick <commit1>..<commitN>

cherry picking parts of a commit (only sections/hunks and not whole files)

git cherry-pick -n <commit> # get your patch, but don't commit (-n = --no-commit)
git reset                   # unstage the changes from the cherry-picked commit
git add -p                  # make all your choices (add the changes you do want)
git commit                  # make the commit!

similar to the above 4 commands - interactive picking (-p == –patch)

git checkout -p <commit>

and if only changes for specific files are wanted:

git checkout -p <commit> -- path/to/file_a path/to/file_b

cherry-pick another git repo (can use sha1 instead of FETCH_HEAD)

git fetch <remote-git-url> <branch> && git cherry-pick FETCH_HEAD

abort the started cherry-pick process, which will revert to the previous state

git cherry-pick --abort

checkout

checkout a specific commit

git checkout <sha1>/or-short-hash

check out a specific branch

git clone https://github.com/vidartf/nbdime -b optimize-diff2

overwrite local changes

If you want to remove all local changes from your working copy, simply stash them:

git stash push --keep-index

or if it’s important you can name it

git stash push "your message here"

to merge the local changes saved with ‘git stash push’ after ‘git pull’

git stash pop

if the merge fails, it doesn’t get removed from the stash.

once merge conflict is manually removed, need to manually call:

git stash drop

If you don’t need them anymore, you now can drop that stash:

git stash drop

to override all local changes and does not require an identity:

git reset --hard
git pull

or:

git checkout -t -f remote/branch
git pull

Discard local changes for a specific file

git checkout dirs-or-files
git pull

maintain current local commits by creating a branch from master before resetting

git checkout master
git branch new-branch-to-save-current-commits
git fetch --all
git reset --hard origin/master

pull from upstream and accept all changes blindly

git pull --strategy theirs

list existing stashes

git stash list

vies stashes:

latest

git stash show -p

specific stash

git stash show -p stash@{0}

show the contents of each stash with one command

git show $(git stash list | cut -d":" -f 1)

diff against a specific stash

git diff stash@{0}

diff against a specific stash’s filename

git diff stash@{0} my/file.ipynb

diff 2 stashes:

git diff stash@{0}..stash@{1}

check out nbdime - diffing and merging of Jupyter Notebooks https://nbdime.readthedocs.io/en/stable/

branches

git branch removal (when not checkout’ed inside the branch that’s about to be removed)

git branch -d branch_name

branch delete via github - after the branch has been merged into the master upsteam, can now delete the branch in my fork at github.com

1. https://github.com/stas00/fastai/branches

or go to https://github.com/stas00/fastai/ (and click [NN branches] above [New pull request] button

1. hit the trash button next to the branch to remove

list branches that are merged or not yet merged to current branch. It’s a useful check before any merging happens

git branch –merged
git branch –no-merged

switch back to last branch (like cd -)

git checkout -

@{-1} is a way to refer to the last branch you were on. ‘-‘ is shorthand for @{-1} git branch --track mybranch @{-1}, git merge @{-1}, and git rev-parse --symbolic-full-name @{-1} would work as expected.

compare two branches in the same repo

git diff --stat --color master..branch_name

or:

git difftool -d master branch_name

find the diff from their common ancestor to test, you can use … instead of ..:

git diff --stat --color master...branch_name

to compare just specific files

git diff branch1 branch2 -- myfile1.js myfile2.js

to compare a sub-directory or specific files across different commits

git diff <rev1>..<rev2> -- dir1 file2

compare two branches in different repos (e.g. original and github fork)

given 2 checkouts /path/to/repoA and /path/to/repoB

cd /path/to/repoA
GIT_ALTERNATE_OBJECT_DIRECTORIES=/path/to/repoB/.git/objects git diff $(git --git-dir=/path/to/repoB/.git rev-parse --verify HEAD) HEAD

another way using GUI with meld (apt install meld)

meld /f1/br/stas00/master/ /f1/br/fastai/master

find the best common ancestor between two branches, usually the branching point:

git merge-base master origin/branch_name

same, but returns a short rev instead of the long one

git rev-parse --short $(git merge-base master origin/branch_name)

alternative (doesn’t always work):

git merge-base --fork-point master origin/branch_name

note that ‘git merge-base’ returns no output once that branch has been merged to master.

diff between the branching point and the HEAD of the branch

git diff $(git merge-base --fork-point master origin/branch_name)..origin/branch_name

commits between the branching point and the HEAD of the branch

git log  --oneline $(git merge-base --fork-point master origin/branch_name)..origin/branch_name

find branches the commit is on

git branch --contains <commit>

find when a commit was merged into one or more branches.

https://github.com/mhagger/git-when-merged

git when-merged [OPTIONS] COMMIT [BRANCH...]

some good docs on branching strategies: https://nvie.com/posts/a-successful-git-branching-model/

reverting/resetting/undoing

lots of scenarios here: https://blog.github.com/2015-06-08-how-to-undo-almost-anything-with-git/

revert the last commit

git revert HEAD

revert everything from the HEAD back to the commit hash 0766c053

git revert --no-commit 0766c053..HEAD
git commit

this will revert everything from the HEAD back to the commit hash, meaning it will recreate that commit state in the working tree as if every commit since had been walked back. You can then commit the current tree, and it will create a brand new commit essentially equivalent to the commit you “reverted” to.

(the --no-commit flag lets git revert all the commits at once- otherwise you’ll be prompted for a message for each commit in the range, littering your history with unnecessary new commits.)

this is a safe and easy way to rollback to a previous state. No history is destroyed, so it can be used for commits that have already been made public.

if merge happened earlier, revert could fail and ask for a specific parent branch via -m flag to specify which mainline to use

for details: http://schacon.github.io/git/howto/revert-a-faulty-merge.txt and https://stackoverflow.com/questions/5970889/why-does-git-revert-complain-about-a-missing-m-option

revert your repository to a specific revision

git checkout <rev>

revert only parts of your repository to a specific revision

git checkout <rev> -- dir1 dir2 file1 file2

Reset branch’s HEAD to a given commit hash

If somehow the HEAD of the branch got messed up and it got moved to some place in master, when someone by mistake merges it into master, here is how to reset it back. In this example we will use a release branch-1.0.36 with a postfix changes applied at a later time, resulting in tag 1.0.36.post.

find the last commit that was supposed to be the HEAD, e.g.: https://github.com/fastai/fastai1/commit/1c63e868d3d11e73d9f51f58cbd271e67a0fe983

Either use this to help find the right commit:
```
git log origin/release-1.0.36
```
or using github’s branch browse of a given tag (1.0.36.post1 in this example).

and now reset the branch’s HEAD to it:

git checkout release-1.0.36
git reset --hard 1c63e868d3
git push --force origin release-1.0.36

ignore

to temporarily ignore changes in a certain file, run:

git update-index --assume-unchanged <file>

track changes again:

git update-index --no-assume-unchanged <file>

trace and debug

check which config comes from where

git config --list --show-origin

display git attributes for a specific path

git check-attr -a dev_nb/001b_fit.ipynb

more here: https://git-scm.com/book/en/v2/Git-Tools-Debugging-with-Git

trace

GIT_TRACE=1 git pull origin master

very verbose

set -x; GIT_TRACE=2 GIT_CURL_VERBOSE=2 GIT_TRACE_PERFORMANCE=2 GIT_TRACE_PACK_ACCESS=2 GIT_TRACE_PACKET=2 GIT_TRACE_PACKFILE=2 GIT_TRACE_SETUP=2 GIT_TRACE_SHALLOW=2 git pull origin master -v -v; set +x

different options:

    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.

status and information

short form log of events

git log --oneline

show a graph of the tree, showing the branch structure of merges

git log --graph --decorate --pretty=oneline --abbrev-commit

add --all to show all branches

show all the commits in a branch that are not in HEAD. e.g. show all commits that are in master but not merged into the current feature branch yet.

git log ..master

overriding git configuration

git -c http.proxy=someproxy clone https://github.com/user/repo.git
git -c [email protected] -c user.name='Your Name'

override git diff:

git diff --no-ext-diff

no such option exists for merge drivers.

fixing things

to fix a bad merge: https://stackoverflow.com/questions/307828/how-do-you-fix-a-bad-merge-and-replay-your-good-commits-onto-a-fixed-merge

“fatal: Unknown index entry format 61740000”.

when your index is broken you can normally delete the index file and reset it.

rm -f .git/index
git reset

or you clone the repo again.

merge strategies

tell git not to merge certain files (i.e. keep the local version) by defining merge filter ‘ours’.

https://stackoverflow.com/a/5895890/9201239

1) add to .gitattributes:

database.xml merge=ours

2) set git merge driver to do nothing but return success

git config merge.ours.name '"always keep ours" merge driver'
git config merge.ours.driver 'touch %A'
git config merge.ours.driver true

workflows

working and updating the local checkout with upstream changes https://stackoverflow.com/questions/457927/git-workflow-and-rebase-vs-merge-questions?rq=1

clone the remote repository
git checkout -b my_new_feature
..work and commit some stuff
git rebase master
..work and commit some stuff
git rebase master
..finish the feature, commit
git rebase master
git checkout master
git merge --squash my_new_feature
git commit -m "added my_new_feature"
git branch -D my_new_feature

Aliases

best to add manually with editor, but can use CLI

.gitconfig
   [alias]

e.g.

git config --global alias.co checkout
git config --global alias.br branch
git config --global alias.ci commit
git config --global alias.st status

unstage a file (equivalent of: git reset HEAD -- fileA:

git config --global alias.unstage 'reset HEAD --'

see last commit

git config --global alias.last 'log -1 HEAD'

use ! for non-git sub-commands in aliases, e.g.:

git config --global alias.visual '!gitk'

git hooks and filters

strip output from Jupyter and IPython notebooks

install nbstripout

pip install nbstripout

check it’s in the path:

which nbstripout

switch to the repository you want to work in

cd fastai_v1/

automatic install for git commit and git diff

nbstripout --install

manual git commit instrumentation

add to .gitattributes or .git/info/attributes:

*.ipynb filter=nbstripout

these will modify .git/config

git config filter.nbstripout.clean `which nbstripout`
git config filter.nbstripout.smudge cat
git config filter.nbstripout.required true

manual git diff instrumentation