Background: I remember driving through the Peak District with snow piled five or six feet high either side of the road as we came off the hills to the converted barn we were staying in. Great snow drifts for the kids, and even with the distractions I learnt all about Git….
All details herin are cribbed from Scott Chacon and Pro Git.
This work is a reminder for the author and in no way represents a full guide, if you want the truth please refer to Scott’s book.
Git stores head ptrs for every snapshot, with ptrs going back through time. A snapshot can be a local branch, a master branch, a remote branch or a tag(non editable snapshot).
Every file (blob) is stored with a SHA-1 hash (checksum), and has a set of files which means it can assocaiate blobs with Sha codes to files and versions. Unlike other version control systems Git has a full history of every file held locally in the .git sub dir. This makes it really quick. You can create branches, switch to them, work, stage the changes, switch to other branches, merge stuff, push and pull stuff from remote repositories all in a hodge podge of collaboration - unlike SVN (say) which has one central repository. Git is famous for being used by Android, Linux Kernal etc. Linux have a Dictator, Lieutenant, developer hierachy which means devs can work on topic branches, Lieutenants merge into their master branches, Dictator merges thier branches into the master branch and then pushes his/her master into the blessed repository.
So, you can have central SVN like repo’s, or you can have peers with their own and resynch as you wish etc. Its all alot more chaotic and you can structure how you work in many ways. Even ignore all that, get going and worry about that stuff later.
Note git does not track files moving between dirs.
There is a short section on Stash at the end of this page.
For workflow, read this: https://www.atlassian.com/git/tutorials/comparing-workflows/feature-branch-workflow (Open in Chrome)
What is SHA-1
40 character string calculated on a hash of the file contents.
Stages of work
You edit a file, you can stash it (preserve it to switch branches).
Or you can stage it - prepare a snapshot of files for the next commmit.Commmit and all staged files are moved permanently into the Git directory.Tracked files were in the last snapshot and can be: unmodified, modified or staged.
/etc/gitconfig values for every user ~/.gitconfig specific for user (c:\Documents and Settings$USER) .git/config specific to the single repository
First time setup
git config --global user.name "John Doe" gif config --global user.email "email@example.com"
git config --global core.editor emacs
git config --global merge.tool vimdiff
What are my settings
git config --list git config user.name
git help <verb> git <verb> --help man git <verb>
Track an existing dir
version control files
git add [wild cards, or file names etc]
eg git add *.java
Starting a server (eg for you to clone on your lan)
git daemon --base-path=/c/2013-dev/javaprojects/ --export-all
Note: where c:/git is the base of all your dev work. and is readonly, for a push access use:
git daemon --base-path=/c/2013-dev/javaprojects/ --export-all --enable=receive-pack
Note: I run this from the Git bash shell, seems to work…
Clone a repo
git clone [url]
depends on the server, so git://, or http(s)://, or user@server:/path.git
Whats going on/
Track new files
git add [filename]
Stage modified files
git add [filename]
NOTE: this stages it at this time, if you edit it again the staged version will NOT include the new edits. Run git add again to include the new edits
How to ignore files
cat .gitignore # comment, this is ignored *.a # no .a files etc etc
What has changed but not staged
What is staged
git diff --staged git diff --cached
Commit the staged stuff
git commit git commit -m "Jire ABC:7676 Fixed the null ptr on user logout"
Commit staged and modified stuff (miss out git add)
git commit -a -m 'a commment'
Remove file from git
git rm [filename]
Force removal of modified file
git rm -f [filename]
Remove a file from Git but keep on disk
git rm --cached [filename]
Move a file
git mv file_from file_to
Note this like using the OS to rename a file and then using git rm, git add
See commmits in reverse order
See changes in each commit
git log -p
Limit log to last x entries
git log -p -2
See abbreviated stats
git log --stat
Log with shorter form
git log --pretty=oneline
–pretty can take short, full and fuller
Log with formatting, eg for auto parsing
git log --pretty=format:"%h - %an"
%H=hash, %h=short hash, %T=tree hash, %t=short tree hash, %P=parent hash, %p=short parent hash, %an=author, %ae=email, %ad=date, %ar=relative date, %cn=committer name, %ce=email, %cd=date, %cr=relative date, %s=subject
Committer is the person promoting towards master branch, author is the author.
See an version graph
git log --pretty=format:"%h %s" --graph
Other log options
-p for patch --stat --shortstat --nameonly --name-status --abbbrev-commit --since=2.weeks --since=2013-03-29 --grep etc etc
To see graphical logs
Changing your last commit
git commmit --amend
You could do a git add prior to this, and the file will be added to the previous commmit.
To unstage a file
git reset HEAD filename
Revert any edits to a modified file
git checkout -- filename
See which remote repos
See remote urls
git remote -v
Add a remote repo
git remote add [remote-name] [url]
Get from remote repo
git fetch [remote-name]
Note that this gets the data, but does not checkout over your work, so you can do this with no risk
Clone to the origin
git clone [url]
This creates a special remote-name called origin. So you could update it using
git fetch origin
Get from remote and merge into your work
Publish your work upstream
git push [remote-name] [branch-name]
So, if you cloned then you have an automatically assigned remote name of origin as your master branch. So to push to where you cloned from
git push origin master
Info on a remote repo
git remote show [remote-name]
Rename a remotes shortname
git remote rename [current name] [new name]
so if it was called jonathan and is now called tony then the branch has changed from jonathan/master to tony/master
Remove reference to remote
git remote rm tony
List tags starting
git tag -l 'v1.4.*'
Create annoted tag
git tag -a v1.4 -m 'My version 1.4'
you could then use git show v1.4 to see details.
Sign a tag with GNU Provacy Guard (GPG)
git tag -s v1.5 -m 'my signed 1.4'
Note that we used -s this time
git tag -v [tag-name]
You need the signers public key for this to work well.
git push [tag-name]
in Git source code download in contrib/completion/git-completion.bash Copy into your home dir and add to .bashrc the line source ~/.git-completion.bash Press tab tab and auto completion should work
git config --global alias.co checkout
would mean you could do git co rather than git checkout
Create a branch
git branch [branch name]
Switch to a branch
get checkout [branch name]
Create branch and switch to it
git checkout -b jira7676
Merge branch back to master
git checkout master git merge jira7676
If the merge can be done with the same history (ie no conflicts) then this is called fast forward.
Delete a branch
git branch -d jira7676
After a merge this will highlight any conflicts, which you can manually fix, look for <<<< and ====== and >>>> You can also use git mergetool
See your branches
See branches and last commit
git branch -v
See whats merged into my current branch
git branch --merged
Branched not merged with work on
git branch --no-merged
Force delete a branch with modifications
git branch -D jira7676
There are commands to create remote branches, rename them, track them and so on, read the book!
Rebasing Rather than merging changes into my current branch, we can go back to the commmon ancestor and reapply the changes from the rebased branch onto my current checked out branch, and then reapply my changes on my current branch. eg you have edits on jira7676 branch, and others have edited master. So
git checkout jira7676 git rebase master git checkout master git merge jira 7676
This will make it look like master has a linear set of checkin’s rater than show a jumble of branches. Very useful if contributing to someone elses master.
git rebase [basebranch] [jira branch]
This is shorthand to replay [jira branch] onto the [basebranch], then you checkout [basebranch] and git merge [jira branch] again.
Do not rebase commmits that you have not pushed to a public repo. If you do you will be changing SHA’s for the same work and messing with your colleagues code - they will have to merge etc.