Git Tips

This entry is part 1 of 3 in the series Version Control

In the last seven months I learned git, working for a dozen of projects. On some of them I was the master&commander, on others I only set up the streams and let the young Jedi find the way to the delivery. Via trial and error I find out a bunch of userful commands.

I present here in order of priority, from the most important to the least…let’s start

 Userful monitoring / configuration  commands

  1. This is the first tip I suggest you:
    git config --global merge.ff false

    This configuration force git to register
    a commit object even if the merge is a fast forward merge.
    Git has a “smart” what of acting, consisting in not registering fast-forward merges. This can be very annoying if you try to track down an evil sith commiting random stuff on your system. Belive me. Sith are so evil!

  2. Find out what happen while you was on holidays…
    git whatchanged  master...my/great-release

    It is the most userful command to check differences between branches/tag/commits.
    If you have a huge project, you can also specify a directory like in

    git whatchanged  master...my/great-release test-scripts-dir

    The standard report is quite good, listing commit comment, and files.
    Even better if you want to recover the previous file’s version,  issue

    git show HEAD^1:parser/src/main/MyStuff.Java >OldStuff.java
    #For two version before try...
    git show HEAD^2:parser/src/main/MyStuff.Java
  3. Resync with remote is always a pain if you forget a branch…
    git remote update

    Without special configuration, this command will fetch updates for all your remotes.
    Very useful if you need to know the status of all your branches

  4. Logs are good, but logs with branch description are better:
    git log --decorate

    Will show you also the branches or the tag

  5. Sometimes you need to erase what you have just commited. An easy way to do it  is
    git reset --soft HEAD^

    This will revert your last commit, leaving it as “Changes to be committed”. Very userful if you do a wrong merge.For instance, if you are on branch “stable” and issue

    git pull origin instableStuff

    you will wrongly issue a merge of the  instableStuff into your stable branch. It is quite subtle.
    Sometimes there is a better option. It is called “revert”:

     git revert HEAD

    is better because will register a “revert” commit on the history, and it is useful when you already pushed your deadly stuff.

    Anyway, “git reflog” will keep in the trashcan the old commit, in case you need it. But be careful,m because reflog is compacted from time to time.

     

Team Caffeine Stats

git shortlog -s -n

Will give you fast stats on your team: is fomeone has a very huge commit rate, reduce free coffe meetings :)

Useful scripting commands

git ls-files
can be used with xargs to kill all your nasty binaries.
For instance
git ls-files workarea/workspace103 | grep /classes/ | xargs git rm
will save your days

Nice to know advices

  • Git 1.7.10 supports utf-8 encoding. I strongly encoruage you to use it instead of older version.
  • –dry-run option
    It is your best friend during a pull or a risky commit. Even if you are better then Yoda (or Linux) at git, you should definitely try it out sometimes.
  • git pull --rebase

    It should avoid merge linearizing input history.
    I am not sure it is a good idea, but can avoid repeating merges if you needn’t. Anyway, do a lot of testing before proceeding in this way.

Subversion to Git migration guide

This Good article
will save your days.

Known weird errors

  • can’t resolve proxy ‘null’ for https
    Do a

    $git var -l | grep http
    http.sslcainfo=/bin/curl-ca-bundle.crt
    http.proxy=

    If you have  the empty http.proxy config, here is the problem.

    Do a look at your $HOME/.gitconfig for the blank http.proxy  configuration, and zap it.

Here you can find other tips.
Hub is a replacement script for git, but I disagree with this approach: anyway, you can decide by yourself if it deserve your attention.

Criptare con emacs

Al giorno d’oggi si hanno tanti account, con tante password. Più una password è diversa dalle altre meglio è. Ma come proteggerle, evitando di segnarne sempre il meno possibile? Sotto MacOSX c’è il Keychain, ovviamente incompatibile con windows e linux.

Grazie a questo articolo, ho scoperto che emacs ha una serie di integrazioni con i meccanismi di criptazione a chiave pubblica e privata. As usual, emacs wins :)

 

Arduino la sfida embedded per il Software Architect

L’Arduino Uno, è un micro controller tutto italiano, sviluppato in open source e che sta avendo un grande successo.

Una parte del suo successo è dovuto al fatto che costa meno di trenta euro, e per essere così economico la versione base ha un chip ATmega328 con soltanto 2 KB di RAM, 1KB di EEPROM e 32KB di memoria flash per il codice. Come implementare comportamenti complessi con risorse così scarse? L’ingegneria del software ci può aiutare?…
Vediamolo assieme, in una serie di articoli che avranno come obiettivo l’ingegnerizzazione spinta del sistema di sviluppo Arduino.

Continue reading “Arduino la sfida embedded per il Software Architect”

Proxy NTLM

Spesso capita di dover scaricare file al di fuori del browser: per esempio per installare software o per consentire ai propri programmi python/java/curl di effettuare delle azioni programmatiche

Se avete problemi con i proxy Microsoft (cosa abbastanza comune, vista la diffusione), su Internet trovate una soluzione:

Cntlm Authentication Proxy vi consente di avere un proxy integrato con il meccanismo non standard usato da Microsoft per autenticarsi. L’utility funziona molto bene, e potete integrarla con cygwin e/o python definendo la seguente variabile d’ambiente

HTTP_PROXY=http://127.0.0.1:3128

Grazie a questo trucco aggiuntivo, il proxy sarà usato da libcurl e da python.

Per Java invece può bastare lanciarlo con

java -Dhttp.proxyHost=127.0.0.1 -Dhttp.proxyPort=3128 classe.da.Lanciare

Junction: symbolic directory links on Windows

Windows 2000 and higher supports directory symbolic links, where a directory serves as a symbolic link to another directory on the computer. […]Directory symbolic links are known as NTFS junctions in Windows. Unfortunately, Windows comes with no tools for creating junctions—you have to purchase the Win2K Resource Kit, which comes with the linkd program for creating junctions. I therefore decided to write my own junction-creating tool: Junction

Continue reading “Junction: symbolic directory links on Windows”