Part 3

Hi folks

SubGit

After the frustration with complicated cherry-picks I decided to try SubGit again

This time I’ve managed to configure it.

Comparing to vanilla git-svn it cloned svn repo much faster.

However, I found that it does not populate svn:mergeinfo metadata on cherry-picks, so there is no point for me to use it.

SmartGit

SmartGit is a good choice. It was a bit challenging to configure it to a non-standard svn layout, but once I did it, it cloned also really quickly.

Moreover, it natively supported svn:mergeinfo… But still I decided not to use it. It is a GUI client, and I am not used to it. I am more GitExtensions user and even more, I am using git from console mostly anyway.

So I haven’t found an use of SmartGit as well

Authors File

Ok, I am coming back to git-svn and handling svn:mergeinfo manually…

After I cloned a repo, I realized that I’ve forgotten to prepare a svn authors file which would map svn author commit info to user names and emails.

I did not want to reclone it again, another 20 hours - no!

So I decided to do this in a git-way.

Firstly I extracted a list of all authors and prepared it in a form git-svn requires

svn-user-name = User Name <User Email>

git log --all --format="%an = %an <%ae>" | Sort-Object -Unique > authors.txt

Then I had some fun trying to understand why it did not work, and after a while I realized that it did not work well with Unicode file and I had so save it as ASCII

git log --all --format="%an = %an <%ae>" | Sort-Object -Unique | Out-File -FilePath authors.txt -Encoding Ascii

It prepared a file like

bobama = bobama <bobama@some-guid>
vputin = vputin <vputin@some-other-guid>
...

So I had to put real names and email there, and I did that manually

bobama = Barak Obama <barak.obama@white-house.gov.us>
vputin = Vladimir Putin <vladimir.putin@kremlin.ru> ...

If we put this file under .git\svn\authors.txt and execute

git config svn.authorsfile .git/svn/authors.txt

next time we do

git fetch

it will map svn user names to real names and emails.

Rewrite Existing Commits

That’s cool, but what about our existing commits with incorrect names and emails?

We’ll have to do a filter-branch. We need only change author name and email, so it is the simplest env-filter

git filter-branch --env-filter="insert bash script here" "--" --all

This bash script should read environment variables that correspond to current commit author name and email and then modify them accordingly.

I don’t know bash at all so initially I though of running PowerShell script that would do all the magic, use the authors.txt we prepared previously.

So I did

git filter-branch --env-filter="PowerShell.exe MyScript.ps1" "--" --all

And none of commits were changed. After a while I realized that when I modify environment variable in a child process (PowerShell) it is not being propagated to the parent process (bash). So unfortunately, I had to write a bash script. And I did not want to get deeper and parse authors.txt file on a fly to extract name and email. So I decided to generate a bash script first.

I used a version found here: http://stackoverflow.com/questions/392332/retroactively-correct-authors-with-git-svn

So here is my generator script

@'
#!/bin/sh

n=$GIT_AUTHOR_NAME
m=$GIT_AUTHOR_EMAIL

case ${GIT_AUTHOR_NAME} in
'@ | Out-File -FilePath MyScript.sh -Encoding Ascii

Get-Content -Path ".git\svn\authors.txt" | `
    Select-String -Pattern "^(?<Alias>[\w._]+) = (?<Name>[\w _]+) \<(?<Email>.*)\>" | `
    ForEach-Object -Process { $_.Matches } | `
    ForEach-Object -Process `
        {
            New-Object -TypeName PSObject -Property `
                @{
                    Alias = $_.Groups["Alias"].Value;
                    Name = $_.Groups["Name"].Val ue;
                    Email = $_.Groups["Email"].Value;
                }
        } |
    ForEach-Object -Process `
        {
@"
        "$($_.Alias)") n="$($_.Name)" ; m="$($_.Email)" ;;
"@
        } | Add-Content -Path MyScript.sh -Encoding Ascii

@'
esac

export GIT_AUTHOR_NAME="$n"
export GIT_AUTHOR_EMAIL="$m"
export GIT_COMMITTER_NAME="$n"
export GIT_COMMITTER_EMAIL="$m"

'@ | Add-Content -Path MyScript.sh -Encoding Ascii

Then we run

git filter-branch --env-filter="MyScript.sh" "--" --all

And funny, it wouldn’t change any commits either for the same reason. Bash is a child process, git is a parent process.

To fix that we’ll need to use a dot-sourcing.

git filter-branch --env-filter=". MyScript.sh" "--" --all

This finally works!

Stay tuned