SVN - 分支

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分支操作建立另一個開發版本。當有人希望將開發過程一分為二時，此功能很有用。假設你已經發布了 1.0 版本的產品，你可能希望建立一個新分支，以便 2.0 的開發可以與 1.0 的錯誤修復分開。

在本節中，我們將瞭解如何建立、遍歷和合並分支。傑瑞對沖突感到不高興，所以他決定建立一個新私有分支。

[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]$

現在傑瑞正在他的私有分支中工作。他為陣列添加了排序操作。傑瑞修改後的程式碼看起來如下。

[jerry@CentOS project_repo]$ cd branches/jerry_branch/

[jerry@CentOS jerry_branch]$ cat array.c

上面的命令將產生以下結果。

#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;
}

傑瑞編譯並測試了他的程式碼，並準備好提交他的更改。

[jerry@CentOS jerry_branch]$ make array
cc     array.c   -o array

[jerry@CentOS jerry_branch]$ ./array

上面的命令將產生以下結果。

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.

與此同時，湯姆決定在主幹中實現搜尋操作。湯姆為搜尋操作添加了程式碼，他的程式碼看起來如下。

[tom@CentOS trunk]$ svn diff

上面的命令將產生以下結果。

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;
 }

在審查後，他提交了他的更改。

[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.

不過湯姆好奇傑瑞在他自己的私有分支中做了什麼。

[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
------------------------------------------------------------------------

透過檢視 Subversion 的日誌訊息，湯姆發現傑瑞實現了“排序”操作。湯姆使用二分查詢演算法實現了搜尋操作，它總是希望資料按排序順序。但是，如果使用者提供的的是未排序順序的資料呢？在這種情況下，二分查詢操作將失敗。因此，他決定使用傑瑞的程式碼在執行搜尋操作之前對資料進行排序。所以他要求 Subversion 將傑瑞分支中的程式碼合併到主幹中。

[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

合併後，array.c 將如下所示。

[tom@CentOS trunk]$ cat array.c

上面的命令將產生以下結果。

#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;
}

在編譯和測試後，湯姆將他的更改提交到了倉庫。

[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]$
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