Branch 选项会给开发者创建出另外一条线路。当有人希望开发进程分开成两条不同的线路时，这个选项会非常有用。我们先假设你已经发布了一个产品的 1.0 版本，你可能想创建一个新的分支，这样就可以不干扰到 1.0 版本的bug修复的同时，又可以开发2.0版本。
在这一节，我们将看到如何创建，穿过和合并分支。Jerry 因为代码冲突的事情不开心，所以他决定创建一个新的私有分支。
[jerry@CentOS project_repo]$ ls
branches tags trunk
[jerry@CentOS project_repo]$ svn copy trunk branches/jerry_branch
A branches/jerry_branch
[jerry@CentOS project_repo]$ svn status
A + branches/jerry_branch
[jerry@CentOS project_repo]$ svn commit -m "Jerry's private branch"
Adding branches/jerry_branch
Adding branches/jerry_branch/README
Committed revision 9.
[jerry@CentOS project_repo]$
现在 Jerry 在自己的分支下开始工作。他给序列添加了 sort 选项。Jerry 修改后的代码如下：
[jerry@CentOS project_repo]$ cd branches/jerry_branch/
[jerry@CentOS jerry_branch]$ cat array.c
上面的代码将会产生下面的结果：
#include <stdio.h>
#define MAX 16
void bubble_sort(int *arr, int n)
{
int i, j, temp, flag = 1;
for (i = 1; i < n && flag == 1; ++i) {
flag = 0;
for (j = 0; j < n - i; ++j) {
if (arr[j] > arr[j + 1]) {
flag = 1;
temp = arr[j];
arr[j] = arr[j + 1];
arr[j + 1] = temp;
}
}
}
}
void accept_input(int *arr, int n)
{
int i;
for (i = 0; i < n; ++i)
scanf("%d", &arr[i]);
}
void display(int *arr, int n)
{
int i;
for (i = 0; i < n; ++i)
printf("|%d| ", arr[i]);
printf("\n");
}
int main(void)
{
int i, n, key, ret, arr[MAX];
printf("Enter the total number of elements: ");
scanf("%d", &n);
/* Error handling for array overflow */
if (n >MAX) {
fprintf(stderr, "Number of elements must be less than %d\n", MAX);
return 1;
}
printf("Enter the elements\n");
accept_input(arr, n);
printf("Array has following elements\n");
display(arr, n);
printf("Sorted data is\n");
bubble_sort(arr, n);
display(arr, n);
return 0;
}
Jerry 编译并且测试了他的代码，准备提交他的更改。
[jerry@CentOS jerry_branch]$ make array
cc array.c -o array
[jerry@CentOS jerry_branch]$ ./array
上面的命令将会产生如下的结果：
Enter the total number of elements: 5
Enter the elements
10
-4
2
7
9
Array has following elements
|10| |-4| |2| |7| |9|
Sorted data is
|-4| |2| |7| |9| |10|
[jerry@CentOS jerry_branch]$ svn status
? array
M array.c
[jerry@CentOS jerry_branch]$ svn commit -m "Added sort operation"
Sending jerry_branch/array.c
Transmitting file data .
Committed revision 10.
同时，越过主干，Tom 决定实现 search 选项。Tom 添加了 search 选项而添加代码，他的代码如下：
[tom@CentOS trunk]$ svn diff
上面的命令将会产生下面的结果：
Index: array.c
===================================================================
--- array.c (revision 10)
+++ array.c (working copy)
@@ -2,6 +2,27 @@
#define MAX 16
+int bin_search(int *arr, int n, int key)
+{
+ int low, high, mid;
+
+ low = 0;
+ high = n - 1;
+ mid = low + (high - low) / 2;
+
+ while (low <= high) {
+ if (arr[mid] == key)
+ return mid;
+ if (arr[mid] > key)
+ high = mid - 1;
+ else
+ low = mid + 1;
+ mid = low + (high - low) / 2;
+ }
+
+ return -1;
+}
+
void accept_input(int *arr, int n)
{
int i;
@@ -22,7 +43,7 @@
int main(void)
{
- int i, n, arr[MAX];
+ int i, n, ret, key, arr[MAX];
printf("Enter the total number of elements: ");
scanf("%d", &n);
@@ -39,5 +60,16 @@
printf("Array has following elements\n");
display(arr, n);
+ printf("Enter the element to be searched: ");
+ scanf("%d", &key);
+
+ ret = bin_search(arr, n, key);
+ if (ret < 0) {
+ fprintf(stderr, "%d element not present in array\n", key);
+ return 1;
+ }
+
+ printf("%d element found at location %d\n", key, ret + 1);
+
return 0;
}
After reviewing, he commits his changes.
[tom@CentOS trunk]$ svn status
? array
M array.c
[tom@CentOS trunk]$ svn commit -m "Added search operation"
Sending trunk/array.c
Transmitting file data .
Committed revision 11.
但是 Tom 好奇 Jerry 在他自己的私有分支中干了什么：
[tom@CentOS trunk]$ cd ../branches/
[tom@CentOS branches]$ svn up
A jerry_branch
A jerry_branch/array.c
A jerry_branch/README
[tom@CentOS branches]$ svn log
------------------------------------------------------------------------
r9 | jerry | 2013-08-27 21:56:51 +0530 (Tue, 27 Aug 2013) | 1 line
Added sort operation
------------------------------------------------------------------------
通过查看 Subversion 的 log 信息，Tom 发现 Jerry 依赖 ‘sort’ 选项。Tom 决定增添用折半查找，期望数据总是根据种类进行分类。但是如果用户提供的数据是没有进行分类呢？在那种情况下，折半查找将会失效。所以他决定接着 Jerry 的代码，在搜索选项前先进性分类。所以他告诉 Subversion 合并 Jerry 的分支到主干中去。
[tom@CentOS trunk]$ pwd
/home/tom/project_repo/trunk
[tom@CentOS trunk]$ svn merge ../branches/jerry_branch/
--- Merging r9 through r11 into '.':
U array.c
在融合后，array.c 会看上去是这个样子：
[tom@CentOS trunk]$ cat array.c
上面的代码将会产生下面的结果：
#include <stdio.h>
#define MAX 16
void bubble_sort(int *arr, int n)
{
int i, j, temp, flag = 1;
for (i = 1; i < n && flag == 1; ++i) {
flag = 0;
for (j = 0; j < n - i; ++j) {
if (arr[j] > arr[j + 1]) {
flag = 1;
temp = arr[j];
arr[j] = arr[j + 1];
arr[j + 1] = temp;
}
}
}
}
int bin_search(int *arr, int n, int key)
{
int low, high, mid;
low = 0;
high = n - 1;
mid = low + (high - low) / 2;
while (low <= high) {
if (arr[mid] == key)
return mid;
if (arr[mid] > key)
high = mid - 1;
else
low = mid + 1;
mid = low + (high - low) / 2;
}
return -1;
}
void accept_input(int *arr, int n)
{
int i;
for (i = 0; i < n; ++i)
scanf("%d", &arr[i]);
}
void display(int *arr, int n)
{
int i;
for (i = 0; i < n; ++i)
printf("|%d| ", arr[i]);
printf("\n");
}
int main(void)
{
int i, n, ret, key, arr[MAX];
printf("Enter the total number of elements: ");
scanf("%d", &n);
/* Error handling for array overflow */
if (n > MAX) {
fprintf(stderr, "Number of elements must be less than %d\n", MAX);
return 1;
}
printf("Enter the elements\n");
accept_input(arr, n);
printf("Array has following elements\n");
display(arr, n);
printf("Sorted data is\n");
bubble_sort(arr, n);
display(arr, n);
printf("Enter the element to be searched: ");
scanf("%d", &key);
ret = bin_search(arr, n, key);
if (ret < 0) {
fprintf(stderr, "%d element not present in array\n", key);
return 1;
}
printf("%d element found at location %d\n", key, ret + 1);
return 0;
}
经过编译和测试后，Tom 提交了他的更改到仓库。
[tom@CentOS trunk]$ make array
cc array.c -o array
[tom@CentOS trunk]$ ./array
Enter the total number of elements: 5
Enter the elements
10
-2
8
15
3
Array has following elements
|10| |-2| |8| |15| |3|
Sorted data is
|-2| |3| |8| |10| |15|
Enter the element to be searched: -2
-2 element found at location 1
[tom@CentOS trunk]$ svn commit -m "Merge changes from Jerry's code"
Sending trunk
Sending trunk/array.c
Transmitting file data .
Committed revision 12.
[tom@CentOS trunk]$