[PATCH v2 4/5] read-cache: update TEST_GIT_INDEX_VERSION support

[Ben Peart <benpeart@microsoft.com>]

Rename TEST_GIT_INDEX_VERSION to GIT_TEST_INDEX_VERSION for consistency with
the other GIT_TEST_ special setups and properly document its use.

Add logic in t/test-lib.sh to give a warning when the old variable is set to
let people know they need to update their environment to use the new
variable.

Signed-off-by: Ben Peart <Ben.Peart@microsoft.com>
---
 Makefile      | 6 +++---
 t/README      | 4 ++++
 t/test-lib.sh | 5 +++--
 3 files changed, 10 insertions(+), 5 deletions(-)

diff --git a/Makefile b/Makefile
index 5a969f5830..9e84ef02f7 100644
--- a/Makefile
+++ b/Makefile
@@ -400,7 +400,7 @@ all::
 # (defaults to "man") if you want to have a different default when
 # "git help" is called without a parameter specifying the format.
 #
-# Define TEST_GIT_INDEX_VERSION to 2, 3 or 4 to run the test suite
+# Define GIT_TEST_INDEX_VERSION to 2, 3 or 4 to run the test suite
 # with a different indexfile format version.  If it isn't set the index
 # file format used is index-v[23].
 #
@@ -2599,8 +2599,8 @@ endif
 ifdef GIT_INTEROP_MAKE_OPTS
 	@echo GIT_INTEROP_MAKE_OPTS=\''$(subst ','\'',$(subst ','\'',$(GIT_INTEROP_MAKE_OPTS)))'\' >>$@+
 endif
-ifdef TEST_GIT_INDEX_VERSION
-	@echo TEST_GIT_INDEX_VERSION=\''$(subst ','\'',$(subst ','\'',$(TEST_GIT_INDEX_VERSION)))'\' >>$@+
+ifdef GIT_TEST_INDEX_VERSION
+	@echo GIT_TEST_INDEX_VERSION=\''$(subst ','\'',$(subst ','\'',$(GIT_TEST_INDEX_VERSION)))'\' >>$@+
 endif
 	@if cmp $@+ $@ >/dev/null 2>&1; then $(RM) $@+; else mv $@+ $@; fi
 
diff --git a/t/README b/t/README
index 47165f7eab..9b13f6d12e 100644
--- a/t/README
+++ b/t/README
@@ -323,6 +323,10 @@ GIT_TEST_FSMONITOR=$PWD/t7519/fsmonitor-all exercises the fsmonitor
 code path for utilizing a file system monitor to speed up detecting
 new or changed files.
 
+GIT_TEST_INDEX_VERSION=<n> exercises the index read/write code path
+for the index version specified.  Can be set to any valid version
+(currently 2, 3, or 4).
+
 Naming Tests
 ------------
 
diff --git a/t/test-lib.sh b/t/test-lib.sh
index 653688c067..397eb71578 100644
--- a/t/test-lib.sh
+++ b/t/test-lib.sh
@@ -134,9 +134,9 @@ export EDITOR
 GIT_TRACE_BARE=1
 export GIT_TRACE_BARE
 
-if test -n "${TEST_GIT_INDEX_VERSION:+isset}"
+if test -n "${GIT_TEST_INDEX_VERSION:+isset}"
 then
-	GIT_INDEX_VERSION="$TEST_GIT_INDEX_VERSION"
+	GIT_INDEX_VERSION="$GIT_TEST_INDEX_VERSION"
 	export GIT_INDEX_VERSION
 fi
 
@@ -159,6 +159,7 @@ check_var_migration () {
 }
 
 check_var_migration GIT_FSMONITOR_TEST GIT_TEST_FSMONITOR
+check_var_migration TEST_GIT_INDEX_VERSION GIT_TEST_INDEX_VERSION
 
 # Add libc MALLOC and MALLOC_PERTURB test
 # only if we are not executing the test with valgrind
-- 
2.18.0.windows.1