Simultaneously, both Harry and Sally have a crisis of conscience and realize that their code has no comments at all.

Harry:

lottery harry$ hg diff
diff -r 922ff5acda79 src/pb.c
--- a/src/pb.c  Tue May 17 14:31:41 2011 -0500
+++ b/src/pb.c  Tue May 17 14:39:21 2011 -0500
@@ -47,6 +47,7 @@
         return -1;
     }
 
+    // lottery ball numbers are always shown sorted
     qsort(white_balls, 5, sizeof(int), my_sort_func);
 
     return 0;

lottery harry$ hg commit -m comments

lottery harry$ hg push
pushing to http://server.futilisoft.com:8000/
searching for changes
remote: adding changesets
remote: adding manifests
remote: adding file changes
remote: added 1 changesets with 1 changes to 1 files

And Sally:

lottery sally$ hg diff
diff -r 836e4df60a27 src/pb.c
--- a/src/pb.c  Tue May 17 14:24:14 2011 -0500
+++ b/src/pb.c  Tue May 17 14:40:27 2011 -0500
@@ -35,7 +35,7 @@
 {
     int balls[6];
     int count_balls = 0;
-    int favorite = 0;
+    int favorite = 0;  // this should be a bool
 
     for (int i=1; i<argc; i++)
     {
@@ -69,10 +69,13 @@
         goto usage_error;
     }
 
+    // the power ball is always the last one given
     int power_ball = balls[5];
 
     int result = calculate_result(balls, power_ball);
 
+    // calculate result can return -1 if the ball numbers
+    // are out of range
     if (result < 0)
     {
         goto usage_error;

lottery sally$ hg commit -m comments

lottery sally$ hg push
pushing to http://server.futilisoft.com:8000/
searching for changes
remote: adding changesets
remote: adding manifests
remote: adding file changes
remote: added 1 changesets with 1 changes to 1 files (+1 heads)

Harry decides to try again to merge the changes from Sally’s branch.

lottery harry$ hg heads
changeset:   21:76fcfc4170dc
branch:      no_boys_allowed
tag:         tip
parent:      17:836e4df60a27
user:        Sally <sally@futilisoft.com>
date:        Tue May 17 14:44:56 2011 -0500
summary:     comments

changeset:   20:6ae39c9ee2e8
user:        Harry <harry@futilisoft.com>
date:        Tue May 17 14:45:04 2011 -0500
summary:     comments

lottery harry$ hg merge -r 21
merging src/pb.c
0 files updated, 1 files merged, 0 files removed, 0 files unresolved
(branch merge, don't forget to commit)

lottery harry$ hg diff
diff -r 6ae39c9ee2e8 src/pb.c
--- a/src/pb.c  Tue May 17 14:45:04 2011 -0500
+++ b/src/pb.c  Tue May 17 14:47:52 2011 -0500
@@ -57,7 +57,7 @@
 {
     int balls[6];
     int count_balls = 0;
-    int favorite = 0;
+    int favorite = 0;  // this should be a bool
 
     for (int i=1; i<argc; i++)
     {
@@ -91,10 +91,13 @@
         goto usage_error;
     }
 
+    // the power ball is always the last one given
     int power_ball = balls[5];
 
     int result = calculate_result(balls, power_ball);
 
+    // calculate result can return -1 if the ball numbers
+    // are out of range
     if (result < 0)
     {
         goto usage_error;

No worries on the merge then. Harry checks to see if everything compiles, and commits the merge.

lottery harry$ make
gcc -std=c99 -Wall -Wextra -Werror pb.c -o pb

lottery harry$ hg commit -m "merge changes from sally"

lottery harry$ hg push
pushing to http://server.futilisoft.com:8000/
searching for changes
remote: adding changesets
remote: adding manifests
remote: adding file changes
remote: added 1 changesets with 1 changes to 1 files (-1 heads)