[PATCH] doc: Improve description for rev-parse --short

[Andreas Heiduk <asheiduk@gmail.com>]

First: `git rev-parse --short` without a number does use a fixed default but
`core.abbrev` which in turn uses `find_unique_abbrev` internally.

Second: `--short` implies `--verify` since the beginning (d50125085a), so
it cannot be used for bulk-shortening ids unfortunately.

Signed-off-by: Andreas Heiduk <asheiduk@gmail.com>
---
 Documentation/config.txt        | 1 +
 Documentation/git-rev-parse.txt | 4 +++-
 2 files changed, 4 insertions(+), 1 deletion(-)

diff --git a/Documentation/config.txt b/Documentation/config.txt
index e0b9fd0bc..158cb588b 100644
--- a/Documentation/config.txt
+++ b/Documentation/config.txt
@@ -862,6 +862,7 @@ core.abbrev::
 	computed based on the approximate number of packed objects
 	in your repository, which hopefully is enough for
 	abbreviated object names to stay unique for some time.
+	The minimum length is 4.
 
 add.ignoreErrors::
 add.ignore-errors (deprecated)::
diff --git a/Documentation/git-rev-parse.txt b/Documentation/git-rev-parse.txt
index c40c47044..7a7421c8e 100644
--- a/Documentation/git-rev-parse.txt
+++ b/Documentation/git-rev-parse.txt
@@ -140,7 +140,9 @@ can be used.
 --short=number::
 	Instead of outputting the full SHA-1 values of object names try to
 	abbreviate them to a shorter unique name. When no length is specified
-	7 is used. The minimum length is 4.
+	the effective value of the configuration variable `core.abbrev` (see
+	linkgit:git-config[1]) is used.  The minimum length is 4.  The length
+	may be exceeded to ensure unique object names.	Implies `--verify`.
 
 --symbolic::
 	Usually the object names are output in SHA-1 form (with
-- 
2.13.0