[PATCH v2] cli/show: make --decrypt take a keyword.

[Daniel Kahn Gillmor <dkg@fifthhorseman.net>]

We also expand tab completion for it, and update T357 to match.

Make use of the bool-to-keyword backward-compatibility feature.
---
 completion/notmuch-completion.bash |  6 +++++-
 doc/man1/notmuch-show.rst          | 37 +++++++++++++++++++++----------------
 notmuch-show.c                     | 22 +++++++++-------------
 test/T357-index-decryption.sh      |  6 +++---
 4 files changed, 38 insertions(+), 33 deletions(-)

diff --git a/completion/notmuch-completion.bash b/completion/notmuch-completion.bash
index fb093de8..4ab2e5f6 100644
--- a/completion/notmuch-completion.bash
+++ b/completion/notmuch-completion.bash
@@ -517,10 +517,14 @@ _notmuch_show()
 	    COMPREPLY=( $( compgen -W "text json sexp mbox raw" -- "${cur}" ) )
 	    return
 	    ;;
-	--exclude|--body|--decrypt)
+	--exclude|--body)
 	    COMPREPLY=( $( compgen -W "true false" -- "${cur}" ) )
 	    return
 	    ;;
+        --decrypt)
+	    COMPREPLY=( $( compgen -W "true auto false" -- "${cur}" ) )
+	    return
+	    ;;
     esac
 
     ! $split &&
diff --git a/doc/man1/notmuch-show.rst b/doc/man1/notmuch-show.rst
index 64caa7a6..7d2b38cb 100644
--- a/doc/man1/notmuch-show.rst
+++ b/doc/man1/notmuch-show.rst
@@ -115,22 +115,27 @@ Supported options for **show** include
         supported with --format=json and --format=sexp), and the
         multipart/signed part will be replaced by the signed data.
 
-    ``--decrypt``
-        Decrypt any MIME encrypted parts found in the selected content
-        (ie. "multipart/encrypted" parts). Status of the decryption will
-        be reported (currently only supported with --format=json and
-        --format=sexp) and on successful decryption the
-        multipart/encrypted part will be replaced by the decrypted
-        content.
-
-        If a session key is already known for the message, then it
-        will be decrypted automatically unless the user explicitly
-        sets ``--decrypt=false``.
-
-        Decryption expects a functioning **gpg-agent(1)** to provide any
-        needed credentials. Without one, the decryption will fail.
-
-        Implies --verify.
+    ``--decrypt=(false|auto|true)``
+        If ``true``, decrypt any MIME encrypted parts found in the
+        selected content (i.e. "multipart/encrypted" parts). Status of
+        the decryption will be reported (currently only supported
+        with --format=json and --format=sexp) and on successful
+        decryption the multipart/encrypted part will be replaced by
+        the decrypted content.
+
+        If ``auto``, and a session key is already known for the
+        message, then it will be decrypted, but notmuch will not try
+        to access the user's keys.
+
+        Use ``false`` to avoid even automatic decryption.
+
+        Non-automatic decryption expects a functioning
+        **gpg-agent(1)** to provide any needed credentials. Without
+        one, the decryption will fail.
+
+        Note: ``true`` implies --verify.
+
+        Default: ``auto``
 
     ``--exclude=(true|false)``
         Specify whether to omit threads only matching
diff --git a/notmuch-show.c b/notmuch-show.c
index d5adc370..9871159d 100644
--- a/notmuch-show.c
+++ b/notmuch-show.c
@@ -1085,8 +1085,6 @@ notmuch_show_command (notmuch_config_t *config, int argc, char *argv[])
     bool exclude = true;
     bool entire_thread_set = false;
     bool single_message;
-    bool decrypt = false;
-    bool decrypt_set = false;
 
     notmuch_opt_desc_t options[] = {
 	{ .opt_keyword = &format, .name = "format", .keywords =
@@ -1101,7 +1099,12 @@ notmuch_show_command (notmuch_config_t *config, int argc, char *argv[])
 	{ .opt_bool = &params.entire_thread, .name = "entire-thread",
 	  .present = &entire_thread_set },
 	{ .opt_int = &params.part, .name = "part" },
-	{ .opt_bool = &decrypt, .name = "decrypt", .present = &decrypt_set },
+	{ .opt_keyword = (int*)(&params.crypto.decrypt), .name = "decrypt",
+	  .keyword_no_arg_value = "true", .keywords =
+	  (notmuch_keyword_t []){ { "false", NOTMUCH_DECRYPT_FALSE },
+				  { "auto", NOTMUCH_DECRYPT_AUTO },
+				  { "true", NOTMUCH_DECRYPT_NOSTASH },
+				  { 0, 0 } } },
 	{ .opt_bool = &params.crypto.verify, .name = "verify" },
 	{ .opt_bool = &params.output_body, .name = "body" },
 	{ .opt_bool = &params.include_html, .name = "include-html" },
@@ -1115,16 +1118,9 @@ notmuch_show_command (notmuch_config_t *config, int argc, char *argv[])
 
     notmuch_process_shared_options (argv[0]);
 
-    if (decrypt_set) {
-	if (decrypt) {
-	    /* we do not need or want to ask for session keys */
-	    params.crypto.decrypt = NOTMUCH_DECRYPT_NOSTASH;
-	    /* decryption implies verification */
-	    params.crypto.verify = true;
-	} else {
-	    params.crypto.decrypt = NOTMUCH_DECRYPT_FALSE;
-	}
-    }
+    /* explicit decryption implies verification */
+    if (params.crypto.decrypt == NOTMUCH_DECRYPT_NOSTASH)
+	params.crypto.verify = true;
 
     /* specifying a part implies single message display */
     single_message = params.part >= 0;
diff --git a/test/T357-index-decryption.sh b/test/T357-index-decryption.sh
index 6b8a8261..2b8e05b8 100755
--- a/test/T357-index-decryption.sh
+++ b/test/T357-index-decryption.sh
@@ -197,14 +197,14 @@ test_expect_equal \
     "$output" \
     "$expected"
 
-test_begin_subtest "show one of the messages with --decrypt"
-output=$(notmuch show --decrypt thread:0000000000000001 | awk '/^\014part}/{ f=0 }; { if (f) { print $0 } } /^\014part{ ID: 3/{ f=1 }')
+test_begin_subtest "show one of the messages with --decrypt=true"
+output=$(notmuch show --decrypt=true thread:0000000000000001 | awk '/^\014part}/{ f=0 }; { if (f) { print $0 } } /^\014part{ ID: 3/{ f=1 }')
 expected='This is a test encrypted message with a wumpus.'
 test_expect_equal \
     "$output" \
     "$expected"
 
-test_begin_subtest "Ensure that we cannot show the message without --decrypt"
+test_begin_subtest "Ensure that we cannot show the message with --decrypt=auto"
 output=$(notmuch show thread:0000000000000001 | awk '/^\014part}/{ f=0 }; { if (f) { print $0 } } /^\014part{ ID: 3/{ f=1 }')
 expected='Non-text part: application/octet-stream'
 test_expect_equal \
-- 
2.15.1