SCM

Git

Configuration

Global configuration:

git config --global user.name    "John Doe"
git config --global user.email   john.doe@example.org
git config --global color.pager  false
git config --global pack.threads 0

To send email via git:

git config --global sendemail.smtpserver mail.example.org
git config --global sendemail.smtpserverport 587

Calculate checksum of remote repository

$ git ls-remote origin
a4c6476651ab11eea605fd09e63acd84bed80284        HEAD
a4c6476651ab11eea605fd09e63acd84bed80284        refs/heads/master
[...]

Calculate checksum of the local repository:

$ git rev-parse HEAD
a4c6476651ab11eea605fd09e63acd84bed80284

Undo a merge:

git checkout master
git fetch origin                                     # May be needed if there are foreign commits in our tree.
git reset --hard [commit-before-the-merge]           # add origin/master to reset to origin/master

dangling tree

git fsck would complain about a dangling tree:

$ git fsck --full --strict
Checking object directories: 100% (256/256), done.
Checking objects: 100% (400/400), done.
dangling tree 85200871abce3a8aef5136f1221ff0267ecca339
dangling tree 5050f6d17066212c805458709f18e099b921fd59

The tree was working perfectly and there's only one tree in this repo anyway. After git gc only one "dangling tree" was left. Another git prune did the trick, no more dangling trees.

set-url

After cloning a local repository, its origin points to the local resource, instead of the remote resource:

$ git clone foo@alice:/usr/local/src/e2fsprogs-git
$ cd e2fsprogs-git
$ git remote -v show
origin  foo@alice:/usr/local/src/e2fsprogs-git (fetch)
origin  foo@alice:/usr/local/src/e2fsprogs-git (push)

Let's see what the original URL was:

alice$ $ git remote -v
origin  git://git.kernel.org/pub/scm/fs/ext2/e2fsprogs.git (fetch)
origin  git://git.kernel.org/pub/scm/fs/ext2/e2fsprogs.git (push)

So, let's change our newly created clone to point to the upstream repository:

$ git remote set-url origin git://git.kernel.org/pub/scm/fs/ext2/e2fsprogs.git

Rewrite history

Rewriting history can be done via git amend. Changing the last commit is easy:

git commit --amend

Changing a commit that is farther back is tricky. Let's rewrite something within the last 3 commits:

git rebase -i HEAD~3
> pick f396a45 abc
> pick 8b29ab1 xxx
> pick cd27e14 yyy

Note: the order here is different from e.g. "git log" and f396a45 is the oldest commit!

In order to change the oldest commit, replace the "pick" to "edit" next to f396a45 and save-exit the editor. Now we can rewrite this commit with:

git commit --amend

With that, rebase can continue:

git rebase --continue

Altering commit data

Altering various commit entities can be accomplished with git filter-branch. Let's alter the commit date as an example:

$ git log -n 1  | head -3
commit 27dba1e90110fd1e7b2429c8b17021ba537c471b
Author: John Doe <doe@example.org>
Date:   Sun Feb 22 14:51:54 2015 -0800

But the file we just commited was from a while back:

$ ls -lgo file.c
-rwx------ 1 2767 Feb  5 01:14 file.c

So we want to alter the commit history to match that file date:

H=27dba1e90110fd1e7b2429c8b17021ba537c471b
D=2015-02-05T01:14:00                                            # See git-commit(1): DATE FORMATS

Let's get the correct date format too:

D=$(date -r file.c +%Y-%m-%dT%H:%M:%S)

Now we can alter the commit:

$ git filter-branch --env-filter "if [ \$GIT_COMMIT = $H ]; then \
    export GIT_AUTHOR_DATE="$D" export GIT_COMMITTER_DATE="$D"; fi"

The commit date has now been changed (and the commit hash too):

$ git log -n 1  | head -3
commit c510521d1668ff8464e91de96d20fc3b6da70c31
Author: John Doe <doe@example.org>
Date:   Thu Feb 5 01:14:00 2015 -0800

The commiter or author can also be changed for a single commit:

H=27dba1e90110fd1e7b2429c8b17021ba537c471b
AN="Me Surname"
AE="me@example.net"
CE="committer@example.net"

git filter-branch --env-filter "if [ \$GIT_COMMIT = $H ]; then \
    export GIT_AUTHOR_NAME="$AN" export GIT_AUTHOR_EMAIL="$AE"; fi"

To rewrite every commit on a branch:

git filter-branch --env-filter "export GIT_AUTHOR_EMAIL=$AE GIT_COMMITTER_EMAIL=$CE" master

git-filter-branch(1) understands GIT_AUTHOR_NAME, GIT_AUTHOR_EMAIL, GIT_AUTHOR_DATE, GIT_COMMITTER_NAME, GIT_COMMITTER_EMAIL and GIT_COMMITTER_DATE

Notes:

• “git filter-branch” successfully used to change committer/author, but changes don't reflect on github
• git push after git filter-branch rejected

Merge commits into one

Multiple commits can be merged like this:

$ git log --pretty=oneline
9ef870fca68ecc80a2f3145ed99ffa3baa5521f1 c
69d2072da98250c5ee9f97359ad582b1e8dceb31 b
5ed10e1c6fc507fcd36955e35d650ee7944700da a

We want to combine commits b & c (the last two commits) into one single commit:

git rebase --interactive HEAD~2
> pick 69d2072 b
> pick 9ef870f c

Change the "pick" to "squash" for the "c" commit, so that it get's combined with its previous commit, b:

> pick 69d2072 b
> squash 9ef870f c

Save & exit from the editor and another editor pops up:

# This is a combination of 2 commits.
# The first commit's message is:
b
# This is the 2nd commit message:
c

Edit as needed and save & quit again. Now the history should look like this:

$ git log --pretty=oneline
98f1c6415f98ff9a12a871bc752b678b41c40e13 b and c
5ed10e1c6fc507fcd36955e35d650ee7944700da a

Convert tarballs into git repository

This can be done as such:

git init
tar -xf ~/foo.tar
git add .
git commit -a -s
rm -rf *

Now the next tarball can be extracted and we continue with "git add" again:

git add .
git commit -a -s
rm -rf *

Continue until all tarballs are integrated into the repository.

Tags

Which tag is a certain commit part of?

git describe --contains c022a0acad534fd5f5d5f17280f6d4d135e74e81
v2.6.36-rc1~300^2~1

So, commit c022a0acad534fd5f5d5f17280f6d4d135e74e81 was introduced in v2.6.36-rc1~300^2~1.

Search

To find the commit that introduced a string:

git log -S foo --source path/to/file                      # Use --all to search the whole repository

Repo size without cloning

For Github repos, their API can be used:

$ curl -s https://api.github.com/repos/git/git | awk '/size/ {print $1, $2, "?B"}'
"size": 481892, ?B

...but we don't know the unit size of this value :-\

CVS to Git

While cvs2git may (or may not) be able to do the job, using git-cvsimport was easier to use and actually worked:

$ cat ~/authorconv
foobar=Foo Bar <foobar@example.org>

$ git cvsimport -v -R -d :pserver:cvs@cvs.example.net:/cvs -A ~/authorconv module

This takes quite some time to complete, but in the end:

$ ls -go .git/cvs-*
-rw-r--r--. 1    94 Apr  8 19:55 .git/cvs-authors
-rw-r--r--. 1 68611 Apr  8 20:12 .git/cvs-revisions

$ git log | grep -c ^commit
712

SVN to Git

Migrating a Subversion repository to Git should be quite straighforward.

Generate the list of authers who commited to the SVN repository:

$ cd ~/project-svn
$ svn log --xml | grep \<author\> | perl -pe 's/.*>(.*?)<.*/$1 = /' | sort -u | tee ~/users.txt
alice = 
bob = 

We have to define mappings for these authors to git-svn can use it:

$ cat ~/users.txt
alice = Alice <alice@example.net>
bob = Bob <bob@example.org>

With ~/users.txt in place, we can import the repository:

mkdir ~/project-git && cd ~/project-git
git svn clone svn://code.example.com/svn/ --authors-file=$HOME/users.txt --no-metadata foobar-git

Now the Git repository should be in place:

$ cd ~/foobar-git
$ git log --max-count=1
commit 8b5d45c20bc9cf490e368bc82f058fb4d9739b2c
Author: Alice <alice@example.net>
Date:   Sat Jan 21 19:24:16 2012 +0000

   fixed something

HTTPS checkout

When checking out over HTTPS:

$ git clone https://github.com/ioerror/tlsdate.git
Cloning into 'tlsdate'...
error: Problem with the SSL CA cert (path? access rights?) while accessing https://github.com/ioerror/tlsdate.git/info/refs
fatal: HTTP request failed

We may have to install the CA certificates first:

apt-get install ca-certificates

Track remote branches

In an already cloned repository, do:

git remote add foobar https://github.com/kelseyhightower/nocode

Fetch objects from the new branch, including tags:

git fetch --tags foobar

List all remote branches:

$ git remote 
foobar
origin

Update remote branch, locally:

git remote update foobar

Update all remote branches, locally:

git checkout master
git remote update

Mercurial

Update a local repository:

hg pull
hg update                                             # Or use -u at the pull command

Delete a branch:

$ hg update -C badbranch                              # update & switch to badbranch
$ hg branches
default                   2922:c7fa97debb36
badbranch                 2924:f58b9c023d3b
$ hg commit --user "joe" --close-branch -m "bogus branch"
$ hg update -C default                                # switch back to the default branch again.

View local changes

hg status

Delete everything but .hg* directories, then checkout a clean copy again

ls -A | grep -v .hg | xargs rm -rf
hg checkout -C

There's also the Purge Extension. Although it's distributed along with Mercurial, it must be activated:

$ cat ~/.hgrc
[extensions]
hgext.purge=

Now hg purge can be used to get rid of untracked objects.

Bazaar

Bazaar seems to be tightly coupled to Launchpad. Checkout out source code requires magical URIs, e.g.:

$ bzr branch lp:gwibber
$ cat gwibber/.bzr/branch/branch.conf 
parent_location = http://bazaar.launchpad.net/~gwibber-committers/gwibber/trunk/

Clean untracked files can be done with Bzrtools:

$ sudo apt-get install bzrtools
$ touch foo bar
$ bzr clean-tree --dry-run
deleting paths:
  bar
  foo

$ bzr clean-tree --force

CVS

Checkout a module of a remote repository:

cvs -d anonymous@cvs.openssl.org:/openssl-cvs co openssl

Update the repository:

cvs update

List all tags in the repository:

cvs -q log -h | awk -F"[.:]" '/^\t/ && $(NF-1)!=0 {print $1}' | sort -u

List all branches in the repository:

cvs -q log -h | awk -F"[.:]" '/^\t/ && $(NF-1)==0 {print $1}' | sort -u

Setting up a CVS server

tbd...

 $CVSROOT/CVRSROOT/passwd
 virtuser:pwcrypt:unixuser unixuser:pwcrypt anonymous::unixuser (no password)
 xinetd user = cvs passenv =

 PAM, if compiled with --enable-pam /etc/pam.d/cvs @include common-auth @include common-account
 no $CVSROOT/CVRSROOT/passwd !
 xinetd user = root passenv =
 client: CVSROOT=:pserver:evil:password@sheep:/var/lib/cvs cvs login cvs co . cvs ls -Rl ./

Subversion

branches & tags

List all branches of a repository by listing the /branches URL. This is often below the same level as /trunk

$ svn info | grep ^URL
URL: http://svn.example.com/svn/trunk

$ svn ls http://svn.example.com/svn/branches/
1.3/
1.4/
1.5/

List all tags:

$ svn ls ^/tags
1.3-release
1.4-release
1.5-release

Checkout a different branch into a new directory:

svn checkout http://svn.example.com/svn/branches/1.5 ../project-version-1.5

Checkout a different tag into a new directory:

svn checkout http://svn.example.com/svn/tags/1.3-release ../project-1.3-release

switch

To change the repository URL, use "switch":

$ svn info | grep ^URL
URL: http://svn.example.com/branches/3.4

$ svn switch http://svn.example.com/branches/3.5

Or, using tag instead of branch:

$ svn ls ^/tags | tail -3
3.3/
3.4/
3.5/

$ svn switch http://svn.example.com/svn/tags/3.5

But what if the repository URL has changed in a more subtle way? E.g. we want to change the branch and the protocol:

$ svn switch https://svn.example.com/branches/3.5
svn: 'http://svn.example.com/branches/3.4' is not the same repository as 'https://svn.example.com'

Hm, lets try relocate then:

$ svn switch --relocate http://svn.example.com/branches/3.4 https://svn.example.com/branches/3.5 .
svn: Relocate can only change the repository part of an URL

However, when we try this in two steps, it seems to work:

svn switch --relocate http://svn.example.com/branches/3.4 https://svn.example.com/branches/3.4 .
svn switch https://svn.example.com/branches/3.5

$ svn info | grep ^URL
URL: http://svn.example.com/branches/3.5

svn:externals

Adding an external repository to an SVN project-directory. For example, adding the WP-reCAPTCHA repo to the Wordpress source tree:

$ cd wp-content/plugins
$ svn propedit svn:externals .
  > wp-recaptcha https://plugins.svn.wordpress.org/wp-recaptcha/trunk/
  > :x
$ svn update
Fetching external item into 'wp-recaptcha'
External at revision 255348.

To add the externals to the SVN root, use the relative path instead:

$ cd wordpress-svn
$ svn propedit svn:externals .
  > wp-content/plugins/wp-recaptcha https://plugins.svn.wordpress.org/wp-recaptcha/trunk/
  > :x
$ svn update

Links

• Git_Guide
• gist - upload code to gist.github.com