t/perf: add perf tests for for-each-ref

Add performance tests for 'for-each-ref'. The tests exercise different
combinations of filters/formats/options, as well as the overall performance
of 'git for-each-ref | git cat-file --batch-check' to demonstrate the
performance difference vs. 'git for-each-ref' with "%(*fieldname)" format
specifiers.

All tests are run against a repository with 40k loose refs - 10k commits,
each having a unique:

- branch
- custom ref (refs/custom/special_*)
- annotated tag pointing at the commit
- annotated tag pointing at the other annotated tag (i.e., a nested tag)

After those tests are finished, the refs are packed with 'pack-refs --all'
and the same tests are rerun.

Signed-off-by: Victoria Dye <vdye@github.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/t/perf/p6300-for-each-ref.sh b/t/perf/p6300-for-each-ref.sh
new file mode 100755 (executable)
index 0000000..fa7289c
--- /dev/null
+++ b/t/perf/p6300-for-each-ref.sh
@@ -0,0 +1,87 @@
+#!/bin/sh
+
+test_description='performance of for-each-ref'
+. ./perf-lib.sh
+
+test_perf_fresh_repo
+
+ref_count_per_type=10000
+test_iteration_count=10
+
+test_expect_success "setup" '
+       test_commit_bulk $(( 1 + $ref_count_per_type )) &&
+
+       # Create refs
+       test_seq $ref_count_per_type |
+               sed "s,.*,update refs/heads/branch_& HEAD~&\nupdate refs/custom/special_& HEAD~&," |
+               git update-ref --stdin &&
+
+       # Create annotated tags
+       for i in $(test_seq $ref_count_per_type)
+       do
+               # Base tags
+               echo "tag tag_$i" &&
+               echo "mark :$i" &&
+               echo "from HEAD~$i" &&
+               printf "tagger %s <%s> %s\n" \
+                       "$GIT_COMMITTER_NAME" \
+                       "$GIT_COMMITTER_EMAIL" \
+                       "$GIT_COMMITTER_DATE" &&
+               echo "data <<EOF" &&
+               echo "tag $i" &&
+               echo "EOF" &&
+
+               # Nested tags
+               echo "tag nested_$i" &&
+               echo "from :$i" &&
+               printf "tagger %s <%s> %s\n" \
+                       "$GIT_COMMITTER_NAME" \
+                       "$GIT_COMMITTER_EMAIL" \
+                       "$GIT_COMMITTER_DATE" &&
+               echo "data <<EOF" &&
+               echo "nested tag $i" &&
+               echo "EOF" || return 1
+       done | git fast-import
+'
+
+test_for_each_ref () {
+       title="for-each-ref"
+       if test $# -gt 0; then
+               title="$title ($1)"
+               shift
+       fi
+       args="$@"
+
+       test_perf "$title" "
+               for i in \$(test_seq $test_iteration_count); do
+                       git for-each-ref $args >/dev/null
+               done
+       "
+}
+
+run_tests () {
+       test_for_each_ref "$1"
+       test_for_each_ref "$1, no sort" --no-sort
+       test_for_each_ref "$1, --count=1" --count=1
+       test_for_each_ref "$1, --count=1, no sort" --no-sort --count=1
+       test_for_each_ref "$1, tags" refs/tags/
+       test_for_each_ref "$1, tags, no sort" --no-sort refs/tags/
+       test_for_each_ref "$1, tags, dereferenced" '--format="%(refname) %(objectname) %(*objectname)"' refs/tags/
+       test_for_each_ref "$1, tags, dereferenced, no sort" --no-sort '--format="%(refname) %(objectname) %(*objectname)"' refs/tags/
+
+       test_perf "for-each-ref ($1, tags) + cat-file --batch-check (dereferenced)" "
+               for i in \$(test_seq $test_iteration_count); do
+                       git for-each-ref --format='%(objectname)^{} %(refname) %(objectname)' refs/tags/ | \
+                               git cat-file --batch-check='%(objectname) %(rest)' >/dev/null
+               done
+       "
+}
+
+run_tests "loose"
+
+test_expect_success 'pack refs' '
+       git pack-refs --all
+'
+run_tests "packed"
+
+test_done