[p4] diff between two revisions

[Robert Cowham]

Hi Jeff

The difference between Subversion and Perforce in this instance is
interesting. 

I personally find it can be very useful to know that (in Perforce) file1 has
10 revisions and file2 has 53 revisions. Of course if I want a consistent
snapshot or configuration then I group them together by specifying a
changelist. However, the difference in revisions between files at the same
changelist is a simple indicator of churn which conveys useful information
at times. Thus I prefer the Perforce distinction - although it does require
a little explanation (particularly if coming from Subversion). It is not im
my experience difficult for people 

When training I tend to use the following definition:

- the history of a file is revisions (each of which has an associated
changelist)
- the history of a folder (or repository) is a list of changelists

Both views are useful at different times.

A couple of other things below:

> Just to wrap this up, the problem was of course my confusion 
> between  revision number and changelist number.  After years 
> of subversion  (where there is no such distinction), the 
> habit is hard to break.
>  
>  My mistake was "confirmed" by the following:
>  
>      terra% p4 diff Makefile#1499 Makefile#1186
>      Makefile#1499 - file(s) up-to-date.
>      Makefile#1186 - file(s) up-to-date.

The diff command compares a file in the workspace against a file in the
repository, so normally you would do "p4 diff Makefile" and it would compare
your local version with the latest (head) revision. If you go "p4 diff
Makefile#1499" it compares your local one with #1499 (if it exists).

In the above case you are performing two comparisons: local Makefile vs.
Makefile#1499 and local Makefile vs. Makefile#1186

Note that diff2 takes 2 arguments, and compares both arguments *in the
repository*.

I agree the message could be clearer - worth emailing support about this.

>  Just try it with any file 'foo' under version control, with 
> any  revision numbers:
>  
>      % p4 diff foo#9999999 foo#100000000
>      foo#9999999 - file(s) up-to-date.
>      foo#100000000 - file(s) up-to-date.
>  
>  Had it not been for this (IMO) misleading output, I likely 
> would have  realized my mistake sooner and would not have 
> bothered this list.
>  What is the meaning of this output, anyway?  Isn't it a bug?

In my view it is not good error handling.

>  Also, I think the unintended 'wrong' answers from a few 
> folks here  regarding '#' verses '@' makes a pretty solid 
> case that the 'revision'
>  and 'changelist number' concepts should be combined (as in  
> subversion).  I don't mean to sound trollish; I just don't 
> see a  compelling reason for the distinction.  If they were 
> combined, my  hassles would have been avoided altogether.

Ah but you are just applying Subversion thinking to Perforce as discussed
above. All systems have their differences.

HTH
Robert