diff --git a/Documentation/git.txt b/Documentation/git.txt
index 7a1d629ca0..6ec871b910 100644
--- a/Documentation/git.txt
+++ b/Documentation/git.txt
@@ -709,6 +709,15 @@ of clones and fetches.
 	the background which do not want to cause lock contention with
 	other operations on the repository.  Defaults to `1`.
 
+`GIT_PRINT_SHA1_ELLIPSIS` (deprecated)::
+	If set to `yes`, print an ellipsis following an
+	(abbreviated) SHA-1 value.  This affects indications of
+	detached HEADs (linkgit:git-checkout[1]) and the raw
+	diff output (linkgit:git-diff[1]).  Printing an
+	ellipsis in the cases mentioned is no longer considered
+	adequate and support for it is likely to be removed in the
+	foreseeable future (along with the variable).
+
 Discussion[[Discussion]]
 ------------------------
 
diff --git a/cache.h b/cache.h
index d74f00d8db..100317823e 100644
--- a/cache.h
+++ b/cache.h
@@ -1942,4 +1942,10 @@ void sleep_millisec(int millisec);
  */
 void safe_create_dir(const char *dir, int share);
 
+/*
+ * Should we print an ellipsis after an abbreviated SHA-1 value
+ * when doing diff-raw output or indicating a detached HEAD?
+ */
+extern int print_sha1_ellipsis(void);
+
 #endif /* CACHE_H */
diff --git a/environment.c b/environment.c
index 8289c25b44..a3abdd3c58 100644
--- a/environment.c
+++ b/environment.c
@@ -343,3 +343,18 @@ int use_optional_locks(void)
 {
 	return git_env_bool(GIT_OPTIONAL_LOCKS_ENVIRONMENT, 1);
 }
+
+int print_sha1_ellipsis(void)
+{
+	/*
+	 * Determine if the calling environment contains the variable
+	 * GIT_PRINT_SHA1_ELLIPSIS set to "yes".
+	 */
+	static int cached_result = -1; /* unknown */
+
+	if (cached_result < 0) {
+		const char *v = getenv("GIT_PRINT_SHA1_ELLIPSIS");
+		cached_result = (v && !strcasecmp(v, "yes"));
+	}
+	return cached_result;
+}
diff --git a/t/t3040-subprojects-basic.sh b/t/t3040-subprojects-basic.sh
index 0a4ff6d824..b81eb5fd6f 100755
--- a/t/t3040-subprojects-basic.sh
+++ b/t/t3040-subprojects-basic.sh
@@ -19,7 +19,7 @@ test_expect_success 'setup: create subprojects' '
 	git update-index --add sub1 &&
 	git add sub2 &&
 	git commit -q -m "subprojects added" &&
-	git diff-tree --abbrev=5 HEAD^ HEAD |cut -d" " -f-3,5- >current &&
+	GIT_PRINT_SHA1_ELLIPSIS="yes" git diff-tree --abbrev=5 HEAD^ HEAD |cut -d" " -f-3,5- >current &&
 	git branch save HEAD &&
 	cat >expected <<-\EOF &&
 	:000000 160000 00000... A	sub1
diff --git a/t/t4013-diff-various.sh b/t/t4013-diff-various.sh
index c515e3e53f..9bed64d53e 100755
--- a/t/t4013-diff-various.sh
+++ b/t/t4013-diff-various.sh
@@ -131,7 +131,7 @@ do
 	test_expect_success "git $cmd" '
 		{
 			echo "\$ git $cmd"
-			git $cmd |
+			GIT_PRINT_SHA1_ELLIPSIS="yes" git $cmd |
 			sed -e "s/^\\(-*\\)$V\\(-*\\)\$/\\1g-i-t--v-e-r-s-i-o-n\2/" \
 			    -e "s/^\\(.*mixed; boundary=\"-*\\)$V\\(-*\\)\"\$/\\1g-i-t--v-e-r-s-i-o-n\2\"/"
 			echo "\$"
diff --git a/t/t9300-fast-import.sh b/t/t9300-fast-import.sh
index d47560b634..e4d06accc4 100755
--- a/t/t9300-fast-import.sh
+++ b/t/t9300-fast-import.sh
@@ -876,7 +876,7 @@ test_expect_success 'L: verify internal tree sorting' '
 	EXPECT_END
 
 	git fast-import <input &&
-	git diff-tree --abbrev --raw L^ L >output &&
+	GIT_PRINT_SHA1_ELLIPSIS="yes" git diff-tree --abbrev --raw L^ L >output &&
 	test_cmp expect output
 '