feat! rename metadata field "sha256" to "label"

The field still contains a cleartext SHa256 of the cleartext chunk
data, but this makes it clearer that it may contain other data.

This is a breaking change: the server API won't work with an old
client, and the new client won't work with an old server. To avoid the
breakage would require more effort than is warranted at this time,
given the very small number of users of Obnam. Sorry.

Sponsored-by: author

1 files changed, 19 insertions, 18 deletions

diff --git a/obnam.md b/obnam.md
index 50c293c..8b80eed 100644
--- a/obnam.md
+++ b/obnam.md
@@ -835,12 +835,13 @@ Chunks consist of arbitrary binary data, a small amount of metadata,
 and an identifier chosen by the server. The chunk metadata is a JSON
 object, consisting of the following fields:
 
-* `sha256` — the SHA256 checksum of the chunk contents as
+* `label` — the SHA256 checksum of the chunk contents as
   determined by the client
   - this MUST be set for every chunk, including generation chunks
   - the server allows for searching based on this field
   - note that the server doesn't verify this in any way, to pave way
-    for future client-side encryption of the chunk data
+    for future client-side encryption of the chunk data, including the
+    label
 * `generation` — set to `true` if the chunk represents a
   generation
   - may also be set to `false` or `null` or be missing entirely
@@ -865,7 +866,7 @@ The server has the following API for managing chunks:
   server, return its randomly chosen identifier
 * `GET /chunks/<ID>` &mdash; retrieve a chunk (and its metadata) from
   the server, given a chunk identifier
-* `GET /chunks?sha256=xyzzy` &mdash; find chunks on the server whose
+* `GET /chunks?label=xyzzy` &mdash; find chunks on the server whose
   metadata indicates their contents has a given SHA256 checksum
 * `GET /chunks?generation=true` &mdash; find generation chunks
 * `GET /chunks?data=True` &mdash; find chunks with file data
@@ -903,7 +904,7 @@ metadata are returned in a JSON object:
 ~~~json
 {
   "fe20734b-edb3-432f-83c3-d35fe15969dd": {
-     "sha256": "09ca7e4eaa6e8ae9c7d261167129184883644d07dfba7cbfbc4c8a2e08360d5b",
+     "label": "09ca7e4eaa6e8ae9c7d261167129184883644d07dfba7cbfbc4c8a2e08360d5b",
      "generation": null,
 	 "ended: null,
   }
@@ -1036,7 +1037,7 @@ storage of backed up data.
 ~~~scenario
 given a working Obnam system
 and a file data.dat containing some random data
-when I POST data.dat to /chunks, with chunk-meta: {"sha256":"abc"}
+when I POST data.dat to /chunks, with chunk-meta: {"label":"abc"}
 then HTTP status code is 201
 and content-type is application/json
 and the JSON body has a field chunk_id, henceforth ID
@@ -1049,17 +1050,17 @@ We must be able to retrieve it.
 when I GET /chunks/<ID>
 then HTTP status code is 200
 and content-type is application/octet-stream
-and chunk-meta is {"sha256":"abc","generation":null,"ended":null}
+and chunk-meta is {"label":"abc","generation":null,"ended":null}
 and the body matches file data.dat
 ~~~
 
 We must also be able to find it based on metadata.
 
 ~~~scenario
-when I GET /chunks?sha256=abc
+when I GET /chunks?label=abc
 then HTTP status code is 200
 and content-type is application/json
-and the JSON body matches {"<ID>":{"sha256":"abc","generation":null,"ended":null}}
+and the JSON body matches {"<ID>":{"label":"abc","generation":null,"ended":null}}
 ~~~
 
 Finally, we must be able to delete it. After that, we must not be able
@@ -1072,7 +1073,7 @@ then HTTP status code is 200
 when I GET /chunks/<ID>
 then HTTP status code is 404
 
-when I GET /chunks?sha256=abc
+when I GET /chunks?label=abc
 then HTTP status code is 200
 and content-type is application/json
 and the JSON body matches {}
@@ -1095,7 +1096,7 @@ We must get an empty result if searching for chunks that don't exist.
 
 ~~~scenario
 given a working Obnam system
-when I GET /chunks?sha256=abc
+when I GET /chunks?label=abc
 then HTTP status code is 200
 and content-type is application/json
 and the JSON body matches {}
@@ -1122,7 +1123,7 @@ First, create a chunk.
 ~~~scenario
 given a working Obnam system
 and a file data.dat containing some random data
-when I POST data.dat to /chunks, with chunk-meta: {"sha256":"abc"}
+when I POST data.dat to /chunks, with chunk-meta: {"label":"abc"}
 then HTTP status code is 201
 and content-type is application/json
 and the JSON body has a field chunk_id, henceforth ID
@@ -1138,10 +1139,10 @@ given a running chunk server
 Can we still find it by its metadata?
 
 ~~~scenario
-when I GET /chunks?sha256=abc
+when I GET /chunks?label=abc
 then HTTP status code is 200
 and content-type is application/json
-and the JSON body matches {"<ID>":{"sha256":"abc","generation":null,"ended":null}}
+and the JSON body matches {"<ID>":{"label":"abc","generation":null,"ended":null}}
 ~~~
 
 Can we still retrieve it by its identifier?
@@ -1150,7 +1151,7 @@ Can we still retrieve it by its identifier?
 when I GET /chunks/<ID>
 then HTTP status code is 200
 and content-type is application/octet-stream
-and chunk-meta is {"sha256":"abc","generation":null,"ended":null}
+and chunk-meta is {"label":"abc","generation":null,"ended":null}
 and the body matches file data.dat
 ~~~
 
@@ -1164,14 +1165,14 @@ server more chatty.
 ~~~scenario
 given a working Obnam system
 and a file data1.dat containing some random data
-when I POST data1.dat to /chunks, with chunk-meta: {"sha256":"qwerty"}
+when I POST data1.dat to /chunks, with chunk-meta: {"label":"qwerty"}
 then the JSON body has a field chunk_id, henceforth ID
 and chunk server's stderr doesn't contain "Obnam server starting up"
 and chunk server's stderr doesn't contain "created chunk <ID>"
 
 given a running chunk server with environment {"OBNAM_SERVER_LOG": "info"}
 and a file data2.dat containing some random data
-when I POST data2.dat to /chunks, with chunk-meta: {"sha256":"xyz"}
+when I POST data2.dat to /chunks, with chunk-meta: {"label":"xyz"}
 then the JSON body has a field chunk_id, henceforth ID
 and chunk server's stderr contains "Obnam server starting up"
 and chunk server's stderr contains "created chunk <ID>"
@@ -1274,8 +1275,8 @@ roots: [live]
 given a working Obnam system
 given a client config based on smoke.yaml
 given a file cleartext.dat containing some random data
-when I run obnam encrypt-chunk cleartext.dat encrypted.dat '{"sha256":"fake"}'
-when I run obnam decrypt-chunk encrypted.dat decrypted.dat '{"sha256":"fake"}'
+when I run obnam encrypt-chunk cleartext.dat encrypted.dat '{"label":"fake"}'
+when I run obnam decrypt-chunk encrypted.dat decrypted.dat '{"label":"fake"}'
 then files cleartext.dat and encrypted.dat are different
 then files cleartext.dat and decrypted.dat are identical
 ~~~