What is the Git equivalent for revision number?

Question

We use SVN at work, but for my personal projects I decided to use Git. So I installed Git yesterday, and I wonder what is the revision number equivalent in Git.

Let's say we work on version 3.0.8 and every bug fix has its own revision number we can use when we talk about this bug fix. So if I tag the code in Git to 3.0.8 what then I can use as a revision number or some other more detailed kind of identification? I find the hash not so user friendly for humans.

Answer 1

Good or bad news for you, that hash IS the revision number. I also had trouble with this when I made the switch from SVN to git.

You can use "tagging" in git to tag a certain revision as the "release" for a specific version, making it easy to refer to that revision. Check out this blog post.

The key thing to understand is that git cannot have revision numbers - think about the decentralized nature. If users A and B are both committing to their local repositories, how can git reasonably assign a sequential revision number? A has no knowledge of B before they push/pull each other's changes.

Another thing to look at is simplified branching for bugfix branches:

Start with a release: 3.0.8. Then, after that release, do this:

git branch bugfixes308

This will create a branch for bugfixes. Checkout the branch:

git checkout bugfixes308

Now make any bugfix changes you want.

git commit -a

Commit them, and switch back to the master branch:

git checkout master

Then pull in those changes from the other branch:

git merge bugfixes308

That way, you have a separate release-specific bugfix branch, but you're still pulling the bugfix changes into your main dev trunk.

Answer 2

The problem with using the git hash as the build number is that it's not monotonically increasing. OSGi suggests using a time-stamp for the build number. It looks like the number of commits to the branch could be used in place of the subversion or perforce change number.

Answer 3

For people who have an Ant build process, you can generate a version number for a project on git with this target:

<target name="generate-version">

    <exec executable="git" outputproperty="version.revisions">
        <arg value="log"/>
        <arg value="--oneline"/>
    </exec>

    <resourcecount property="version.revision" count="0" when="eq">
        <tokens>
            <concat>
                <filterchain>
                    <tokenfilter>
                        <stringtokenizer delims="\r" />
                    </tokenfilter>
                </filterchain>
            <propertyresource name="version.revisions" />
            </concat>
        </tokens>
    </resourcecount>
    <echo>Revision : ${version.revision}</echo>

    <exec executable="git" outputproperty="version.hash">
        <arg value="rev-parse"/>
        <arg value="--short"/>
        <arg value="HEAD"/>
    </exec>
    <echo>Hash : ${version.hash}</echo>


    <exec executable="git" outputproperty="version.branch">
        <arg value="rev-parse"/>
        <arg value="--abbrev-ref"/>
        <arg value="HEAD"/>
    </exec>
    <echo>Branch : ${version.branch}</echo>

    <exec executable="git" outputproperty="version.diff">
        <arg value="diff"/>
    </exec>

    <condition property="version.dirty" value="" else="-dirty">
        <equals arg1="${version.diff}" arg2=""/>
    </condition>

    <tstamp>
        <format property="version.date" pattern="yyyy-mm-dd.HH:mm:ss" locale="en,US"/>
    </tstamp>
    <echo>Date : ${version.date}</echo>

    <property name="version" value="${version.revision}.${version.hash}.${version.branch}${version.dirty}.${version.date}" />

    <echo>Version : ${version}</echo>

    <echo file="version.properties" append="false">version = ${version}</echo>

</target>

The result looks like this:

generate-version:
    [echo] Generate version
    [echo] Revision : 47
    [echo] Hash : 2af0b99
    [echo] Branch : master
    [echo] Date : 2015-04-20.15:04:03
    [echo] Version : 47.2af0b99.master-dirty.2015-04-20.15:04:03

The dirty flag is here when you have file(s) not committed when you generate the version number. Because usually, when you build/package your application, every code modification has to be in the repository.

Answer 4

The git describe command creates a slightly more human readable name that refers to a specific commit. For example, from the documentation:

With something like git.git current tree, I get:

[torvalds@g5 git]$ git describe parent
v1.0.4-14-g2414721

i.e. the current head of my "parent" branch is based on v1.0.4, but since it has a few commits on top of that, describe has added the number of additional commits ("14") and an abbreviated object name for the commit itself ("2414721") at the end.

As long as you use sensibly named tags to tag particular releases, this can be considered to be roughly equivalent to a SVN "revision number".

Answer 5

I wrote some PowerShell utilities for retrieving version information from Git and simplifying tagging

functions: Get-LastVersion, Get-Revision, Get-NextMajorVersion, Get-NextMinorVersion, TagNextMajorVersion, TagNextMinorVersion:

# Returns the last version by analysing existing tags,
# assumes an initial tag is present, and
# assumes tags are named v{major}.{minor}.[{revision}]
#
function Get-LastVersion(){
  $lastTagCommit = git rev-list --tags --max-count=1
  $lastTag = git describe --tags $lastTagCommit
  $tagPrefix = "v"
  $versionString = $lastTag -replace "$tagPrefix", ""
  Write-Host -NoNewline "last tagged commit "
  Write-Host -NoNewline -ForegroundColor "yellow" $lastTag
  Write-Host -NoNewline " revision "
  Write-Host -ForegroundColor "yellow" "$lastTagCommit"
  [reflection.assembly]::LoadWithPartialName("System.Version")

  $version = New-Object System.Version($versionString)
  return $version;
}

# Returns current revision by counting the number of commits to HEAD
function Get-Revision(){
   $lastTagCommit = git rev-list HEAD
   $revs  = git rev-list $lastTagCommit |  Measure-Object -Line
   return $revs.Lines
}

# Returns the next major version {major}.{minor}.{revision}
function Get-NextMajorVersion(){
    $version = Get-LastVersion;
    [reflection.assembly]::LoadWithPartialName("System.Version")
    [int] $major = $version.Major+1;
    $rev = Get-Revision
    $nextMajor = New-Object System.Version($major, 0, $rev);
    return $nextMajor;
}

# Returns the next minor version {major}.{minor}.{revision}
function Get-NextMinorVersion(){
    $version = Get-LastVersion;
    [reflection.assembly]::LoadWithPartialName("System.Version")
    [int] $minor = $version.Minor+1;
    $rev = Get-Revision
    $next = New-Object System.Version($version.Major, $minor, $rev);
    return $next;
}

# Creates a tag with the next minor version
function TagNextMinorVersion($tagMessage){
    $version = Get-NextMinorVersion;
    $tagName = "v{0}" -f "$version".Trim();
    Write-Host -NoNewline "Tagging next minor version to ";
    Write-Host -ForegroundColor DarkYellow "$tagName";
    git tag -a $tagName -m $tagMessage
}

# Creates a tag with the next major version (minor version starts again at 0)
function TagNextMajorVersion($tagMessage){
    $version = Get-NextMajorVersion;
    $tagName = "v{0}" -f "$version".Trim();
    Write-Host -NoNewline "Tagging next majo version to ";
    Write-Host -ForegroundColor DarkYellow "$tagName";
    git tag -a $tagName -m $tagMessage
}

Answer 6

If you're interested, I managed version numbers automatically from git infos here under the format

<major>.<minor>.<patch>-b<build>

where build is the total number of commits. You'll see the interesting code in the Makefile. Here is the relevant part to access the different part of the version number:

LAST_TAG_COMMIT = $(shell git rev-list --tags --max-count=1)
LAST_TAG = $(shell git describe --tags $(LAST_TAG_COMMIT) )
TAG_PREFIX = "latex-tutorial-v"

VERSION  = $(shell head VERSION)
# OR try to guess directly from the last git tag
#VERSION    = $(shell  git describe --tags $(LAST_TAG_COMMIT) | sed "s/^$(TAG_PREFIX)//")
MAJOR      = $(shell echo $(VERSION) | sed "s/^\([0-9]*\).*/\1/")
MINOR      = $(shell echo $(VERSION) | sed "s/[0-9]*\.\([0-9]*\).*/\1/")
PATCH      = $(shell echo $(VERSION) | sed "s/[0-9]*\.[0-9]*\.\([0-9]*\).*/\1/")
# total number of commits       
BUILD      = $(shell git log --oneline | wc -l | sed -e "s/[ \t]*//g")

#REVISION   = $(shell git rev-list $(LAST_TAG).. --count)
#ROOTDIR    = $(shell git rev-parse --show-toplevel)
NEXT_MAJOR_VERSION = $(shell expr $(MAJOR) + 1).0.0-b$(BUILD)
NEXT_MINOR_VERSION = $(MAJOR).$(shell expr $(MINOR) + 1).0-b$(BUILD)
NEXT_PATCH_VERSION = $(MAJOR).$(MINOR).$(shell expr $(PATCH) + 1)-b$(BUILD)