This is great, Julian. It is pretty good for a draft. I'll get back to
you with the detailed answers tonight - just wanted to give my thumbs up.
I'm ok with a simpler solution that just sets the attributes on commit,
but what you have described looks like a good step up from the minimum
and solves additional requirements which fall under "would be nice" for
me... Thanks!
On 01/04/2012 01:42 PM, Julian Foad wrote:
Hi Mark.
I think I can see to some extent what you are getting at, but not clearly. We
all need a common frame of reference for understanding why and how some sort of
extended author information could be useful. To help us get there, I put
together the following tentative proposal to act as a basis for
discussion. Perhaps we can now move on to talking about specific requirements
and designs. What parts of it are aligned with your thinking and what
have I got wrong or missed out?
Please note that this draft is purely an invention of my mind and I do not
expect it to be an accurate reflection of your or anyone else's requirements.
A PROPOSAL FOR EXTENDED AUTHOR IDENTIFICATION
USE CASES
1.[This one I am aware of.]
A large company has authenticated user ids that are numeric. That means the "log" and
"blame" information shown by most Subversion clients is not easy to understand.
Therefore they use a (post-commit?) hook to change
the svn:author property to a more friendly string, which (mostly) solves the
display issue. However, it causes other problems. [What problems?]
2. [This one is a guess.]
The leader of a small development team sharing a Subversion repository with
other teams wants to set up a build slave that will send an email to the users
who committed revisions leading to a build failure. The machine can see the
Subversion user id but how can it get the user's email address? The team
leader could ask the repository administrator to add a post-commit hook that
adds an email address to a revision property after every commit, but that
* requires involving the server admin;
* won't get updated when the user changes their email address;
* won't work for testing old revisions that were already committed before
that time;
* won't work if the build slave software needs to read a list of all user
id->email mappings at once.
3. [This one is a guess.]
An administrator wants to integrate Subversion with an issue tracker. Users
have different user ids on the two tools. The admin wants to configure the
tracker so that it automatically annotates an already committed Subversion
revision with some status information. How can the tracker know with what user
id to contact the Subversion server?
The rest of the proposal addresses UC1 and part of UC2 but not UC3. (UC3 looks
like it needs some totally separate solution, outside of Subversion.)
REQUIREMENTS
A Subversion client (of any kind so designed) shall be able to read extended
information about the author of a revision. This information shall consist of
a (possibly empty) set of fields. The set of possible extended author fields
shallinclude at least:
* authenticated user id
* display name
* email address
It shall be possible to add other fields on the server side (by software
upgrade and/or by configuration), and for a client (of any kind so designed) to
discover and read these fields without any software upgrade on the client side.
The svn:author property shall continue to exist. When not using the
extended author fields, the svn:author property must continue to operate as
before. When using the extended author fields, the design may restrict the use
of the svn:author field. Example: the design could require that if extended
author fields are to be usable then the svn:author field always holds the
authenticated user id and must always be present and non-empty.
A client shall access the extended author fields through the Subversion
server, through the existing client-server protocols, possibly with protocol
extensions. Any protocol extensions shall be backward compatible in that an
old server with a new client or an old client with a new server shall (without
user intervention) use the old 'svn:author' property.
The fields that are available from a particular server or repository are
determined by the administrator. For any particular committed revision, the
server may provide any or all or none of the extended author fields. A client
cannot rely on any particular field being available except to the extent that
the administrator gives such an assurance. Example: if the client requests the
authenticated user id and email address for a revision whose author has no
email address recorded,the server shall provide the authenticated user id but
no email address. If the server is temporarily unable to look up any
information about a user, the server should respond with no extended author
fieldsinstead of waiting.
The extended author fields are dynamic in the sense that the server need not always return the same values
for the same committed revision. For example,a client might repeat exactly the same request for information
about revision 1234 twice in quick succession, and the server might provide the email address as
"a@b.c" the first time and "d...@ee.ff" the second time. Even the "authenticated
user id" field could change.
DESIGN
The extended author fields are delivered through revision properties. The
values are UTF-8 text. These revision properties are readable but not writable
by clients.
Three property names are initially designated as "well known":
* prop name: "svn:author:authn-id"
purpose: authenticated user id
format: as used by Subversion's authentication (the default
value of svn:author)
* prop name: "svn:author:display-name"
purpose: display name
format: a single line (no line breaks), e.g. person's full
name or shortened name or nickname
* prop name: "svn:author:email"
purpose: email address
format: [TO BE SPECIFIED HERE]
Other property names in this name space beginning with "svn:author:" can be designated
as "well known" in the future, by an official announcement from the Subversion project.
An administrator can configure other extended author fields to use property names that are not
in the "svn:" name space. Example: an administrator could configure the property name
"author:pgp-sig" to hold the author's PGP signature.
SERVER DESIGN
Any time the server is about to send a set of revision properties to
the client, the server looks up the extended author fields and adds
corresponding properties to the set of revision properties that it
reports to the client. These property values override any values The server looks up the
extended author fieldsthrough some mechanism not defined here,using the value of
the"svn:author" property as a key. The server may cache the results, provided
that there is a way for the administrator to make the server use updated information.
If the client attempts to set any revision property in the "svn:author:"
name space, the server shall report an error to the client. This applies even if the
property value matches the value that was last read from the server or is currently known
to the server, and even if the
specific property name is not known to the server. If the client attempts to set any
revision property that is not in the "svn:author:" name space but might be
configured as an extended author field, the server records that revision property in the
normal way. If a revision property (of any name) has a stored value and the extended
author field look-up also provides a value for the same property name, the latter takes
priority.
The extended author fields [are | are not] available to the following hook
scripts: pre-commit, ...
CLIENT DESIGN
Just an example. The "svn log" and "svn blame" commands could request the revision property named
"svn:author:display-name", and if that is returned then use it instead of "svn:author", otherwise use the value of
"svn:author". Further, a client-side configuration option could specify which property name should be used for these display purposes, so
for example some users in a particular team could choose to have the "author:nickname" revision property displayed instead of
"svn:author:display-name".
FURTHER SCOPE
Does a client need to be able to look up the information in other ways, such
as starting from svn:author rather than a revision number, or starting from an
extended author field?
- Julian
--
Mark Mielke<m...@mielke.cc>
