Merge branch 'jc/maint-mailinfo-mime-attr'

When "git am" is fed an input that has multiple "Content-type: ..."
header, it did not grok charset= attribute correctly.

* jc/maint-mailinfo-mime-attr:
  mailinfo: do not concatenate charset= attribute values from mime headers

diff --cc builtin/mailinfo.c
Simple merge

diff --cc t/t5100/sample.mbox
Simple merge