[PATCH v2] doc: fix the max number of git show-branches shown

From: wonda-tea-coffee <lagrange.resolvent@gmail.com>

The number to be displayed is calculated by the following defined in object.h.

```
  #define REV_SHIFT        2
  #define MAX_REVS        (FLAG_BITS - REV_SHIFT)
```

FLAG_BITS is currently 28, so 26 is the correct number.

Signed-off-by: Rikita Ishikawa <lagrange.resolvent@gmail.com>
---
    doc: fix the max number of git show-branches shown
    
    Changes since v1:
    
     * Explain in the commit message why "26" is the correct number.

Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-1757%2Fwonda-tea-coffee%2Fupdate-git-show-branch-description-v2
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-1757/wonda-tea-coffee/update-git-show-branch-description-v2
Pull-Request: https://github.com/gitgitgadget/git/pull/1757

Range-diff vs v1:

 1:  b809d610a36 ! 1:  6fc335807d2 doc: fix the max number of git show-branches shown
     @@ Metadata
       ## Commit message ##
          doc: fix the max number of git show-branches shown
      
     -    Contrary to the number listed in the current document,
     -    only 26 are actually shown.
     +    The number to be displayed is calculated by the
     +    following defined in object.h.
      
     -    Signed-off-by: wonda-tea-coffee <lagrange.resolvent@gmail.com>
     +    ```
     +      #define REV_SHIFT        2
     +      #define MAX_REVS        (FLAG_BITS - REV_SHIFT)
     +    ```
     +
     +    FLAG_BITS is currently 28, so 26 is the correct
     +    number.
     +
     +    Signed-off-by: Rikita Ishikawa <lagrange.resolvent@gmail.com>
      
       ## Documentation/git-show-branch.txt ##
      @@ Documentation/git-show-branch.txt: Shows the commit ancestry graph starting from the commits named

 Documentation/git-show-branch.txt | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)