[PATCH] fix potential infinite loop given large unsigned integer

given n, tried to find i greater than n via i=1, iterate i *= 10.
given n sufficiently close to UINT_MAX this will overflow; which can
produce i==0, which results in an infinite loop. iteratively dividing
n /= 10 does not have this problem, and though division is slower than
multiplication this only runs once per `git format-patch
--cover-letter`

Signed-off-by: pizza <redacted>
---
 log-tree.c |    6 +++---
 1 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/log-tree.c b/log-tree.c
index 6f73c17..53a1bd2 100644
--- a/log-tree.c
+++ b/log-tree.c

@@ -160,9 +160,9 @@ static void append_signoff(struct strbuf *sb,

const char *signoff)

 static unsigned int digits_in_number(unsigned int number)
 {
-       unsigned int i = 10, result = 1;
-       while (i <= number) {
-               i *= 10;
+       unsigned int result = 1;
+       while (number > 9) {
+    number /= 10;
                result++;
        }
        return result;
-- 
1.6.0.4