Merge branch 'maint-1.5.4' into maint

* maint-1.5.4:
git-bisect: make "start", "good" and "skip" succeed or fail atomically
git-am: cope better with an empty Subject: line
Ignore leading empty lines while summarizing merges
bisect: squelch "fatal: ref HEAD not a symref" misleading message
builtin-apply: Show a more descriptive error on failure when opening a patch
Clarify documentation of git-cvsserver, particularly in relation to git-shell

diff --cc Documentation/git-cvsserver.txt
Simple merge

diff --cc builtin-apply.c
Simple merge

diff --cc builtin-fmt-merge-msg.c
Simple merge

diff --cc git-am.sh
index ac5c388060789e559f80d61d6eae1db926b66ad4,0f05a2cfe301126a5390b3886f054f23c803e91c..245e1db1fc30c9446f42ae6b4626de854062afc7
--- 1/git-am.sh
--- 2/git-am.sh
+++ b/git-am.sh
@@@ -117,13 -117,8 +117,9 @@@ It does not apply to blobs recorded in 
      unset GITHEAD_$his_tree
  }
  
- reread_subject () {
-       git stripspace <"$1" | sed -e 1q
- }
- 
  prec=4
 -dotest=.dotest sign= utf8=t keep= skip= interactive= resolved= binary=
 +dotest=".dotest"
 +sign= utf8=t keep= skip= interactive= resolved= binary= rebasing=
  resolvemsg= resume=
  git_apply_opt=
  

diff --cc git-bisect.sh
Simple merge

diff --cc t/t6030-bisect-porcelain.sh
Simple merge