Meanwhile, Sally is fixin’ to go ahead and add a feature that was requested by the sales team: If the user chooses the lucky number 7 as the red ball, the chances of winning are doubled. Since she is starting a new task, she decides to begin with pull and update to make sure she has the latest code.
lottery sally$ vv pull Pulling from http://server.futilisoft.com:8080/repos/lottery: Pulling... Done. lottery sally$ vv update lottery sally$ vv parents Parents of pending changes in working copy: revision: 5:ee2493eac8e7fc751e2b57a87a3768a192770ae3 branch: master who: harry when: 2011/05/31 10:25:47.532 -0500 comment: merge parent: 4:7290fd8b3372dfecf5622dec12284d602553258e parent: 3:7414ae0aa096674df94e6f3e142e893709ff3ac6
Then she implements the lucky 7 feature in two shakes of a lamb’s tail by
adding just a few lines
of new code to main().
lottery sally$ vv diff === ================ === Modified: File @/lottery.c --- @/lottery.c e3d1f5b0034e4d190e76b993e67d3e2bd24072ed +++ @/lottery.c 2011/05/31 15:27:06.000 +0000 @@ -44,6 +44,11 @@ int result = calculate_result(white_balls, power_ball); + if (7 == power_ball) + { + result = result * 2; + } + printf("%d percent chance of winning\n", result); return 0;
And commits her change. And pushes it too.
lottery sally$ vv commit -m "lucky 7" revision: 6:d494106a9a796e4887aa8de464d825aa76a59a0b branch: master who: sally when: 2011/05/31 10:27:31.083 -0500 comment: lucky 7 parent: 5:ee2493eac8e7fc751e2b57a87a3768a192770ae3 lottery sally$ vv push Pushing to http://server.futilisoft.com:8080/repos/lottery: Pushing... Done.
Meanwhile, Harry has realised his last change had a bug. He modified
calculate_result() to return -1 for invalid arguments but he forgot to modify
the caller to handle the error. As a consequence, entering a ball number that is
out of range causes the program to behave improperly.
lottery harry$ ./a.out 61 2 3 4 5 42 -1 percent chance of winning
The percent chance of winning certainly can’t be a negative number, now can it? So Harry adds an extra check for this case.
lottery harry$ vv diff === ================ === Modified: File @/lottery.c --- @/lottery.c e3d1f5b0034e4d190e76b993e67d3e2bd24072ed +++ @/lottery.c 2011/05/31 15:28:08.000 +0000 @@ -44,6 +44,12 @@ int result = calculate_result(white_balls, power_ball); + if (result < 0) + { + fprintf(stderr, "Invalid arguments\n"); + return -1; + } + printf("%d percent chance of winning\n", result); return 0;
And proceeds to commit and push the fix.
lottery harry$ vv commit -m "propagate error code" revision: 6:dc13f09452dbc1e24d2ad68b1fba917ef1856b61 branch: master who: harry when: 2011/05/31 10:28:33.769 -0500 comment: propagate error code parent: 5:ee2493eac8e7fc751e2b57a87a3768a192770ae3 lottery harry$ vv push vv: Error 234 (sglib): The branch needs to be merged.
Blimey! Sally must have pushed a new changeset already. Harry once again needs to pull and merge to combine Sally’s changes with his own.
lottery harry$ vv pull Pulling from http://server.futilisoft.com:8080/repos/lottery: Pulling... Done. lottery harry$ vv heads revision: 7:d494106a9a796e4887aa8de464d825aa76a59a0b branch: master who: sally when: 2011/05/31 10:27:31.083 -0500 comment: lucky 7 parent: 5:ee2493eac8e7fc751e2b57a87a3768a192770ae3 revision: 6:dc13f09452dbc1e24d2ad68b1fba917ef1856b61 branch: master who: harry when: 2011/05/31 10:28:33.769 -0500 comment: propagate error code parent: 5:ee2493eac8e7fc751e2b57a87a3768a192770ae3
lottery harry$ vv merge 1 updated, 0 deleted, 0 added, 1 merged, 1 unresolved
The merge didn’t go quite as smoothly this time.
Harry wonders if anyone would notice if he were to take the Wumpty down to the pub. Apparently there
was a conflict.
Harry decides to
open up lottery.c in his editor to examine the situation.
...
int result = calculate_result(white_balls, power_ball);
<<<<<<< Baseline: BASELINE~lottery.c: /Users/harry/lottery/.sgdrawer/t/merge_2011...
if (result < 0)
{
fprintf(stderr, "Invalid arguments\n");
return -1;
}
=======
if (7 == power_ball)
{
result = result * 2;
}
>>>>>>> Other: OTHER~lottery.c: /Users/harry/lottery/.sgdrawer/t/merge_2011...
printf("%d percent chance of winning\n", result);
return 0;
...
Veracity has included both Harry’s code and Sally’s code with conflict markers to delimit things. What we want is to include both blocks of code. Sally’s new code can simply be included right after Harry’s error checking.
...
int result = calculate_result(white_balls, power_ball);
if (result < 0)
{
fprintf(stderr, "Invalid arguments\n");
return -1;
}
if (7 == power_ball)
{
result = result * 2;
}
printf("%d percent chance of winning\n", result);
return 0;
...
That should take care of the problem. Harry compiles the code to make sure and then commits the merge.
lottery harry$ vv commit -m "merge" vv: Error 202 (sglib): Cannot commit with unresolved merge issues.
Crikey! Now what? Harry fixed the conflict in lottery.c but
Veracity doesn’t seem to know that.
lottery harry$ vv resolve list Unresolved contents conflict on File: @/lottery.c Baseline Path: @/lottery.c Problem: Merge couldn't generate the item's contents. Cause(s): Edit/Edit: Changes to item's contents in different branches conflict. Possible Contents: (use 'view' or 'diff' to examine) ancestor baseline other merge: automatically merged from 'baseline' and 'other' with ':merge' working
Ah yes. Harry realises that he forgot to tell Veracity that he had resolved the conflict. He uses resolve to let Veracity know that the problem has been dealt with.
lottery harry$ vv resolve accept working lottery.c Accepted 'working' value for 'contents' conflict on File: @/lottery.c lottery harry$ vv resolve list
There, that looks much better. Harry tries again to commit the merge.
lottery harry$ vv commit -m "merge" revision: 8:817b33a44fd16f268c6bd0f75b95aaf32e461554 branch: master who: harry when: 2011/05/31 10:29:50.892 -0500 comment: merge parent: 7:d494106a9a796e4887aa8de464d825aa76a59a0b parent: 6:dc13f09452dbc1e24d2ad68b1fba917ef1856b61
And then to retry the push.
lottery harry$ vv push Pushing to http://server.futilisoft.com:8080/repos/lottery: Pushing... Done.
That’s put paid to that.