builtin/describe.c |    2 +-
 cache.h            |    5 +++--
 config.c           |    8 ++++++++
 environment.c      |    1 +
 4 files changed, 13 insertions(+), 3 deletions(-)

diff --git a/builtin/describe.c b/builtin/describe.c
index 43caff2..2d98702 100644
--- a/builtin/describe.c
+++ b/builtin/describe.c
@@ -20,7 +20,7 @@ static int debug;	/* Display lots of verbose info */
 static int all;	/* Any valid ref can be used */
 static int tags;	/* Allow lightweight tags */
 static int longformat;
-static int abbrev = DEFAULT_ABBREV;
+static int abbrev = 7;	/* NOTE! Not DEFAULT_ABBREV */
 static int max_candidates = 10;
 static int found_names;
 static const char *pattern;
diff --git a/cache.h b/cache.h
index 33decd9..6c28a81 100644
--- a/cache.h
+++ b/cache.h
@@ -540,6 +540,7 @@ extern int trust_executable_bit;
 extern int trust_ctime;
 extern int quote_path_fully;
 extern int has_symlinks;
+extern int minimum_abbrev, default_abbrev;
 extern int ignore_case;
 extern int assume_unchanged;
 extern int prefer_symlink_refs;
@@ -757,8 +758,8 @@ static inline unsigned int hexval(unsigned char c)
 }
 
 /* Convert to/from hex/sha1 representation */
-#define MINIMUM_ABBREV 4
-#define DEFAULT_ABBREV 7
+#define MINIMUM_ABBREV minimum_abbrev
+#define DEFAULT_ABBREV default_abbrev
 
 struct object_context {
 	unsigned char tree[20];
diff --git a/config.c b/config.c
index 4b0a820..474361c 100644
--- a/config.c
+++ b/config.c
@@ -514,6 +514,14 @@ static int git_default_core_config(const char *var, const char *value)
 		return 0;
 	}
 
+	if (!strcmp(var, "core.abbrev")) {
+		int abbrev = git_config_int(var, value);
+		if (abbrev < minimum_abbrev || abbrev > 40)
+			return -1;
+		default_abbrev = abbrev;
+		return 0;
+	}
+
 	if (!strcmp(var, "core.loosecompression")) {
 		int level = git_config_int(var, value);
 		if (level == -1)
diff --git a/environment.c b/environment.c
index de5581f..b98003c 100644
--- a/environment.c
+++ b/environment.c
@@ -15,6 +15,7 @@ int user_ident_explicitly_given;
 int trust_executable_bit = 1;
 int trust_ctime = 1;
 int has_symlinks = 1;
+int minimum_abbrev = 4, default_abbrev = 7;
 int ignore_case;
 int assume_unchanged;
 int prefer_symlink_refs;