[PATCH 2/4] config doc: unify the description of fsck.* and receive.fsck.*

["Ævar Arnfjörð Bjarmason" <avarab@gmail.com>]

The documentation for the fsck.<msg-id> and receive.fsck.<msg-id>
variables was mostly duplicated in two places, with fsck.<msg-id>
making no mention of the corresponding receive.fsck.<msg-id>, and the
same for fsck.skipList.

I spent quite a lot of time today wondering why setting the
fsck.<msg-id> variant wasn't working to clone a legacy repository (not
that that would have worked anyway, but a subsequent patch implements
fetch.fsck.<msg-id>).

Rectify this situation by describing the feature in general terms
under the fsck.* documentation, and make the receive.fsck.*
documentation refer to those variables instead.

This documentation was initially added in 2becf00ff7 ("fsck: support
demoting errors to warnings", 2015-06-22) and 4b55b9b479 ("fsck:
document the new receive.fsck.<msg-id> options", 2015-06-22).

Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
---
 Documentation/config.txt | 74 ++++++++++++++++++++++------------------
 1 file changed, 41 insertions(+), 33 deletions(-)

diff --git a/Documentation/config.txt b/Documentation/config.txt
index 623dffd198..351c541ab8 100644
--- a/Documentation/config.txt
+++ b/Documentation/config.txt
@@ -1554,23 +1554,41 @@ filter.<driver>.smudge::
 	linkgit:gitattributes[5] for details.
 
 fsck.<msg-id>::
-	Allows overriding the message type (error, warn or ignore) of a
-	specific message ID such as `missingEmail`.
-+
-For convenience, fsck prefixes the error/warning with the message ID,
-e.g.  "missingEmail: invalid author/committer line - missing email" means
-that setting `fsck.missingEmail = ignore` will hide that issue.
-+
-This feature is intended to support working with legacy repositories
-which cannot be repaired without disruptive changes.
+	During fsck git may find issues with legacy data which
+	wouldn't be generated by current versions of git, and which
+	wouldn't be sent over the wire if `transfer.fsckObjects` was
+	set. This feature is intended to support working with legacy
+	repositories containing such data.
++
+Setting `fsck.<msg-id>` will be picked up by linkgit:git-fsck[1], but
+to accept pushes of such data set `receive.fsck.<msg-id>` instead. The
+rest of the documentation discusses `fsck.*` for brevity, but the same
+applies for the corresponding `receive.fsck.*` variables.
++
+When `fsck.<msg-id>` is set, errors can be switched to warnings and
+vice versa by configuring the `fsck.<msg-id>` setting where the
+`<msg-id>` is the fsck message ID and the value is one of `error`,
+`warn` or `ignore`. For convenience, fsck prefixes the error/warning
+with the message ID, e.g. "missingEmail: invalid author/committer line
+- missing email" means that setting `fsck.missingEmail = ignore` will
+hide that issue.
++
+Depending on the circumstances it might be better to use
+`fsck.skipList` instead to explicitly whitelist those objects that
+have issues, otherwise new occurrences of the same issue will be
+hidden going forward, although that's unlikely to happen in practice
+unless someone is being deliberately malicious.
 
 fsck.skipList::
-	The path to a sorted list of object names (i.e. one SHA-1 per
-	line) that are known to be broken in a non-fatal way and should
-	be ignored. This feature is useful when an established project
-	should be accepted despite early commits containing errors that
-	can be safely ignored such as invalid committer email addresses.
-	Note: corrupt objects cannot be skipped with this setting.
+	Like `fsck.<msg-id>` this variable has a corresponding
+	`receive.fsck.skipList` variant.
++
+The path to a sorted list of object names (i.e. one SHA-1 per line)
+that are known to be broken in a non-fatal way and should be
+ignored. This feature is useful when an established project should be
+accepted despite early commits containing errors that can be safely
+ignored such as invalid committer email addresses. Note: corrupt
+objects cannot be skipped with this setting.
 
 gc.aggressiveDepth::
 	The depth parameter used in the delta compression
@@ -2849,26 +2867,16 @@ receive.fsckObjects::
 	`transfer.fsckObjects` is used instead.
 
 receive.fsck.<msg-id>::
-	When `receive.fsckObjects` is set to true, errors can be switched
-	to warnings and vice versa by configuring the `receive.fsck.<msg-id>`
-	setting where the `<msg-id>` is the fsck message ID and the value
-	is one of `error`, `warn` or `ignore`. For convenience, fsck prefixes
-	the error/warning with the message ID, e.g. "missingEmail: invalid
-	author/committer line - missing email" means that setting
-	`receive.fsck.missingEmail = ignore` will hide that issue.
-+
-This feature is intended to support working with legacy repositories
-which would not pass pushing when `receive.fsckObjects = true`, allowing
-the host to accept repositories with certain known issues but still catch
-other issues.
+	Acts like `fsck.<msg-id>`, but is used by
+	linkgit:git-receive-pack[1] instead of
+	linkgit:git-fsck[1]. See the `fsck.<msg-id>` documentation for
+	details.
 
 receive.fsck.skipList::
-	The path to a sorted list of object names (i.e. one SHA-1 per
-	line) that are known to be broken in a non-fatal way and should
-	be ignored. This feature is useful when an established project
-	should be accepted despite early commits containing errors that
-	can be safely ignored such as invalid committer email addresses.
-	Note: corrupt objects cannot be skipped with this setting.
+	Acts like `fsck.skipList`, but is used by
+	linkgit:git-receive-pack[1] instead of
+	linkgit:git-fsck[1]. See the `fsck.skipList` documentation for
+	details.
 
 receive.keepAlive::
 	After receiving the pack from the client, `receive-pack` may
-- 
2.17.0.290.gded63e768a