api-trace.txt: add trace API documentation

diff --git a/Documentation/config.txt b/Documentation/config.txt
index bdce52981dbcb12e6dfb82c175d2ca169b53a4be..9f467d3820a40d1281d29707e98fa16c2bbde63f 100644 (file)
--- a/Documentation/config.txt
+++ b/Documentation/config.txt
@@ -621,9 +621,9 @@ core.preloadindex::
 +
 This can speed up operations like 'git diff' and 'git status' especially
 on filesystems like NFS that have weak caching semantics and thus
-relatively high IO latencies.  With this set to 'true', Git will do the
+relatively high IO latencies.  When enabled, Git will do the
 index comparison to the filesystem data in parallel, allowing
-overlapping IO's.
+overlapping IO's.  Defaults to true.
 
 core.createObject::
        You can set this to 'link', in which case a hardlink followed by
@@ -1122,6 +1122,10 @@ format.signature::
        Set this variable to the empty string ("") to suppress
        signature generation.
 
+format.signaturefile::
+       Works just like format.signature except the contents of the
+       file specified by this variable will be used as the signature.
+
 format.suffix::
        The default for format-patch is to output files with the suffix
        `.patch`. Use this variable to change that suffix (make sure to