Tag Archives: git

Exporting GIT repositories remotely

This tip may be useful for those working on a local GIT tree, but in need to “export” it to a remote server (for example for building and testing).

I know that ideally one would “push” the changes to a commonly-accessible remote server, and pull back from the build/testing host. But sometimes we simply don’t have GIT available on that host, other times we’re just lazy.

The standard procedure then is to use the “git archive” command to export the contents of the repository to a tarball, optionally compress it, and then transfer it and unpack on the remote side:

$ git archive --format=tar --prefix=kernel_20101221a/ HEAD | bzip2 > kernel_20101221a.tar.bz2
$ scp kernel_20101221a.tar.bz2 root@spin.ltc.br.ibm.com:.
root@spin.ltc.br.ibm.com's password:
kernel_20101221a.tar.bz2                                                  100%   68MB  11.4MB/s   00:06    
$ ssh root@spin.ltc.br.ibm.com
root@spin.ltc.br.ibm.com's password:
Last login: Tue Dec 21 15:01:59 2010 from dyn531363.br.ibm.com
# tar xvf kernel_20101221a.tar.bz2
kernel_20101221a/
kernel_20101221a/.gitignore
kernel_20101221a/.mailmap
kernel_20101221a/COPYING
kernel_20101221a/CREDITS
kernel_20101221a/Documentation/
kernel_20101221a/Documentation/.gitignore
kernel_20101221a/Documentation/00-INDEX
kernel_20101221a/Documentation/ABI/
...

This has obvious problems… Even if you’re using SSH key authentication to avoid entering the password twice, you end-up typing too many commands and transferring too many bytes. For a project as large as the Linux kernel, this could be a real pain.

A smarter, more direct alternative would be to avoid creating a local archive at all, using ssh input/output tunneling and tar to do the hard-lifting for us:

$ git archive --format=tar --prefix=kernel_20101221b/ HEAD | ssh root@spin.ltc.br.ibm.com tar xvf -
root@spin.ltc.br.ibm.com's password:
kernel_20101221b/
kernel_20101221b/.gitignore
kernel_20101221b/.mailmap
kernel_20101221b/COPYING
kernel_20101221b/CREDITS
kernel_20101221b/Documentation/
kernel_20101221b/Documentation/.gitignore
kernel_20101221b/Documentation/00-INDEX
kernel_20101221b/Documentation/ABI/
kernel_20101221b/Documentation/ABI/README
...

Since you may end-up doing this several times per day, an even smarter way would be to just transfer the absolute necessary – essentially what changed between the last and the current tree. RSYNC is the ideal tool to do that, since it will only send the differences between those files. We could, in theory, use rsync to transfer the whole tree, perhaps ignoring the .git directory since it has no use for us remotely. An even better option would be to transfer just what’s being tracked (and rsync would transfer just what changed). Doing that requires us to use “git ls-files” to list the files being tracked, and pipe that to a rsync command that reads the files to be transfered from standard input:

$ git ls-files -z | rsync -e ssh --files-from - -av0 . root@spin.ltc.br.ibm.com:kernel_20101221c/
root@spin.ltc.br.ibm.com's password:
building file list ... done
Documentation/
Documentation/ABI/
Documentation/ABI/obsolete/
Documentation/ABI/removed/
Documentation/ABI/stable/
Documentation/ABI/testing/
Documentation/DocBook/
Documentation/DocBook/drm.tmpl
Documentation/DocBook/filesystems.tmpl
Documentation/DocBook/gadget.tmpl
Documentation/DocBook/genericirq.tmpl
Documentation/DocBook/kernel-api.tmpl
Documentation/DocBook/kernel-hacking.tmpl
Documentation/DocBook/kernel-locking.tmpl
Documentation/DocBook/kgdb.tmpl
Documentation/DocBook/libata.tmpl
Documentation/DocBook/librs.tmpl
Documentation/DocBook/lsm.tmpl
Documentation/DocBook/mcabook.tmpl
Documentation/DocBook/media-entities.tmpl
Documentation/DocBook/media-indices.tmpl
Documentation/DocBook/media.tmpl
...

The “git ls-files” command will list only the files being tracked in the current git tree. The “-z” argument for “git ls-files”, together with it’s counterpart “-0” in the rsync command tell those commands to use “\0” (the null character) as delimiter between files, so that is safe to deal with file names with spaces on them.

The final step is to create an alias that will invoke the command above:

$ git config --add alias.upload-spin '!git ls-files -z | rsync -e ssh --files-from - -av0 . root@spin.ltc.br.ibm.com:kernel-dev/'
$ git upload-spin
root@spin.ltc.br.ibm.com's password:
building file list ... done
created directory kernel-dev

Note that “shell” aliases (i.e., starting with “!”) will execute those commands on the top-level directory for the GIT repository you are on, so the command above should work correctly even from sub-directories.

I hope the above tips can increase your productivity when working with cross-platform development (and more important, freeing you from a boring repetitive task to more do more value-add coding).

Leave a comment if you like it, have corrections or would like to show us some other tips.

-Klaus

Update:

Sometimes you’ll need a clean upload, meaning you’d like to remove untracked files from the remote side. Turns out this is not as easy as I have hoped.

I’m using the the output from “git ls-files” as an “inclusion filter”, plus an “include all dirs” and a “exclude everything” filter to the rsync command. The reasons why I’m using those are beyond the scope of this post (check the INCLUDE/EXCLUDE PATTERN RULES section at the rsync(1) man page), but the command below seems do to the trick:

git ls-files -z | rsync -avi0 -e ssh --include-from - --include '*/' --prune-empty-dirs \
    --delete --delete-excluded --exclude '*' . root@spin.ltc.br.ibm.com:kernel-dev/

I’ve created an alias called “update-pristine” that does that automatically for me. It will take more time to execute than the original version (I believe due to recursive path descend), but again, you should only use it when wanting to explicitly exclude everything that is not being tracked.

Reviewing patches

I always struggled at reviewing code.

Specially when the code to be reviewed is in reality a patch inlined in some e-mail… I hate monospaced fonts in my e-mail reader, and with all the context switches I got in my daily work, I simply can’t concentrate properly in order to follow what’s been proposed with that one patch out of many, in that long long patch series.

In the past, I used to apply them manually, then go over the code using Source Navigator and later cscope.

I still miss the ability to jump between symbol definition and use that cscope does the best, but I have a much more streamlined way of reviewing patches today, thanks to git, meld, and claws-mail.

The first thing is about git. Nowadays I use git in every coding project I use – even if the upstream project is not using git as SCM itself (I simply create a local repository and import). And this is not only for making reviewing patches easier, but all sorts of things, like fast branching and merging, easy cherry-picking, rebasing, commit amending, modern utilities et al. It’s really the 21st century version control system.

The second thing is meld. Meld is one good example of an intuitive interface that doesn’t get in the way. It can compare, merge and edit files (up to 3-way merge if needed). Supports all the major SCMs such as git, hg, cvs and svn (although I can’t find a reason why would anyone still use the last two, at least locally).

Meld side-by-side diff
Meld side-by-side diff

The forth thing, and where actually everything makes sense, is Claws-mail, which has the very useful (and unique?) ability to create custom actions to process messages.

Claws-Mail Actions
Claws-Mail Actions

Guess what happens when you combine Claws-Mail’s actions with a script that uses git and Meld? A very point-and-click way of reviewing patches:

Claws-Mail, git and Meld in action
Claws-Mail, git and Meld in action

The trick is in configuring an action in Claws-Mail that opens a terminal and calls a script. The script uses git-am to apply the patch contained within the selected mail message to some branch in your local git repository. After applying, it calls git-difftool to show the differences. git-difftool then calls any diff tool you might like (my suggestion stays with Meld).

I’m attaching the script for reference below:

#!/bin/sh
## git-review-step
## (C) Copyright 2010 Klaus Heinrich Kiwi
## Licensed under CreativeCommons Attribution-ShareAlike 3.0 Unsupported
## http://creativecommons.org/licenses/by-sa/3.0/ for more info.
 
## dirname is where the git tree is located.
dirname=$HOME/sandbox/ock/sourceforge-git/opencryptoki
 
if [ "$#" -lt 1 ]; then
  echo "Invalid number of parameters"
  echo "usage: $(basename $0) <patch1> [patch2] [patch3] [...]"
  exit 1
fi
 
messages=($@)
 
cd $dirname
oldbranch=`git branch | grep -e '^* ' | cut -d " " -f 2`
 
# Save any uncommitted changes in the working dir or index
if git stash | grep HEAD; then
  savedchanges="yes"
fi
 
function restore() {
  echo "Reverting to original branch..."
  git checkout --force $oldbranch
  if [ -n "$savedchanges" ]; then
    echo "Restoring un-committed changes..."
    git stash pop
  fi
}
 
# Get branch to apply to
git branch
echo "Select branch to apply patches:"
echo "  Enter \"<branchname>\" to apply to an existing branch"
echo "  Enter \"<newname> [origref]\" to create a new branch from \"origref\""
echo "    reference (use current branch and HEAD if left blank)"
read -p "Apply patch(es) to branch (default is current):" -e -i $oldbranch newbranch origbranch
 
if [ -n "$newbranch" ]; then
  if git branch | grep -e "\b${newbranch}$"; then
    echo "Applying to existing branch \"$newbranch\""
    # Checkout
    if ! git checkout $newbranch; then
      echo "Error checkout out \"$newbranch\" - Aborting"
      restore
      read -p "Press Enter to continue"
      exit 1
    fi
  else
    if [ -n "$origbranch" ]; then
      echo "Applying to new branch \"$newbranch\" created from \"$origbranch\" branch..."
    else
      echo "Applying to new branch \"$newbranch\" created from \"$oldbranch\" branch..."
    fi
    if ! git checkout -b $newbranch $origbranch; then
      echo "Error creating \"$newbranch\" from \"$oldbranch\" - Aborting"
      restore
      read -p "Press Enter to continue"
      exit 1
    fi  # if ! git checkout ...
 
  fi    # if `git branch | grep ...
 
fi      # if [ -n $newbranch ...
 
# Apply patches to working dir using git-apply
amparams="--whitespace=error-all"
while ! git am $amparams ${messages[@]}; do
  git am --abort
  echo "git-am failed. Retry (the whole chunk) with additional parameters?"
  read -p "git-am parameters (empty aborts):" -e -i $amparams amparams
  if [ -z "$amparams" ]; then
    echo "Aborting..."
    restore
    read -p "Press Enter to continue"
    exit 1
  fi
done
 
for (( i=${#messages[@]}; i > 0; i-- )); do
  PAGER='' git log --stat HEAD~${i}..HEAD~$((i-1))
  if git diff --check HEAD~${i}..HEAD~$((i-1)); then
    echo "WARNING: Commit introduces whitespace or indenting errors"
  fi
  git difftool HEAD~${i}..HEAD~$((i-1))
done
 
echo "Restoring working tree to original state"
restore
read -p "Press Enter to continue"

Creative Commons License
git-review-step by Klaus Heinrich Kiwi is licensed under a Creative Commons Attribution-ShareAlike 3.0 Unported License.
Based on a work at blog.klauskiwi.com.