Re: which version control supports file locking and who has it locked

On Mon, Jun 6, 2016 at 3:47 PM, Doug Robinson <doug.robinson_at_wandisco.com>
wrote:

> Andreas:
>
> On Mon, Jun 6, 2016 at 3:50 AM, Andreas Stieger <Andreas.Stieger_at_gmx.de>
> wrote:
>
>> > or knowing who is actually working on a file.
>>
>> Incorrect, this is shown in both TortoiseSVN and svn cli.
>>
>
> To be more precise, you can know who, in the past, has made changes to
> files
> *and*checked those change into the repository. You cannot know who has
> made changes
> in their working copy and has not yet checked them back into the
> repository (they
> may never do so).
>
> To know who is actually working on a file requires a level of integration
> that is not
> found in SVN, Git or CVS. I have a vague recollection of an SCM that did
> enable
> such information but I'm not remembering which one it is at the moment.
>
>
​Whether it is possible to know who is working on a file is not the same as
what the changes made so far in the working copy are. This IS possible
without much problems with at least CVS with minor effort: By setting a
watch on a module alle files in that module are checked out read only.
Before changing a file one uses the CVS edit command, that takes care of
making the file read/write and keep track of who edits what. I'm not
entirely sure if this is the behavior the SVN implementation supports.
Off course it is possible to ignore the read-only flag and use operating
system tools to overwrite them without first using the edit command, but as
long as everyone involved knows the tools this works very well and
accidents are unlikely because files are read-only by default. The only
problem might be you only find out you had not yet edited a file the first
time you save changes and fixing that requires either a habit change (the
new habit being either first edit or save early, save often, which is a
good idea anyway) or a simple trigger in your IDE.

We have used this CVS feature with success in the past for source files
that require 'exclusive edits' because merging was next-to-impossible (as
would be the case for many binary file.) When we migrated to Subversion for
unrelated reasons I couldn't quite get it to work like we wanted (if I
remember correctly taking a lock was more on a voluntary basis, you
couldn't make the files read-only by default and therefore accidentally
forgetting to lock was far more likely.) So I ended up implementing an edit
trigger in the IDE to handle this, which works fine for our use case but
might not be possible in other setups.

I don't see how it could be implemented in a DVCS though, at least not
without a non-distributed part added to it which defeats at least some of
its purpose.

As for other systems supporting this functionality, to answer the original
question: At least Microsoft TFS and Roundtable TSMS (a platform intended
specifically for OpenEdge ABL) support it to some extent. This being said,
I wouldn't pick any of these or CVS over something like Subversion, GIT or
Mercurial if I were to make the choice.

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