fast-export: allow seeding the anonymized mapping

After you anonymize a repository, it can be hard to find which commits
correspond between the original and the result, and thus hard to
reproduce commands that triggered bugs in the original.

Let's make it possible to seed the anonymization map. This lets users
either:

  - mark names to be retained as-is, if they don't consider them secret
    (in which case their original commands would just work)

  - map names to new values, which lets them adapt the reproduction
    recipe to the new names without revealing the originals

The implementation is fairly straight-forward. We already store each
anonymized token in a hashmap (so that the same token appearing twice is
converted to the same result). We can just introduce a new "seed"
hashmap which is consulted first.

This does make a few more promises to the user about how we'll anonymize
things (e.g., token-splitting pathnames). But it's unlikely that we'd
want to change those rules, even if the actual anonymization of a single
token changes. And it makes things much easier for the user, who can
unblind only a directory name without having to specify each path within
it.

One alternative to this approach would be to anonymize as we see fit,
and then dump the whole refname and pathname mappings to a file. This
does work, but it's a bit awkward to use (you have to manually dig the
items you care about out of the mapping).

Helped-by: Eric Sunshine <sunshine@sunshineco.com>
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 10 insertions, 1 deletions

diff --git a/t/t9351-fast-export-anonymize.sh b/t/t9351-fast-export-anonymize.sh
index dc5d75cd19..5a21c71568 100755
--- a/t/t9351-fast-export-anonymize.sh
+++ b/t/t9351-fast-export-anonymize.sh
@@ -6,6 +6,7 @@ test_description='basic tests for fast-export --anonymize'
 test_expect_success 'setup simple repo' '
 	test_commit base &&
 	test_commit foo &&
+	test_commit retain-me &&
 	git checkout -b other HEAD^ &&
 	mkdir subdir &&
 	test_commit subdir/bar &&
@@ -18,7 +19,10 @@ test_expect_success 'setup simple repo' '
 '
 
 test_expect_success 'export anonymized stream' '
-	git fast-export --anonymize --all >stream
+	git fast-export --anonymize --all \
+		--anonymize-map=retain-me \
+		--anonymize-map=xyzzy:custom-name \
+		>stream
 '
 
 # this also covers commit messages
@@ -30,6 +34,11 @@ test_expect_success 'stream omits path names' '
 	! grep xyzzy stream
 '
 
+test_expect_success 'stream contains user-specified names' '
+	grep retain-me stream &&
+	grep custom-name stream
+'
+
 test_expect_success 'stream omits gitlink oids' '
 	# avoid relying on the whole oid to remain hash-agnostic; this is
 	# plenty to be unique within our test case