$brew doctor を実行した結果。(現在、 brew install git が失敗する）

brew_doctor

$ brew doctor
Unbrewed dylibs were found in /usr/local/lib.

If you didn't put them there on purpose they could cause problems when
building Homebrew formulae, and may need to be deleted.

Unexpected dylibs:
    /usr/local/lib/libasprintf.0.dylib
    /usr/local/lib/libcharset.1.0.0.dylib
    /usr/local/lib/libexpat.1.5.2.dylib
    /usr/local/lib/libgettextlib-0.18.dylib
    /usr/local/lib/libgettextpo.0.dylib
    /usr/local/lib/libgettextsrc-0.18.dylib
    /usr/local/lib/libiconv.2.2.0.dylib
    /usr/local/lib/libintl.8.dylib

Unbrewed static libraries were found in /usr/local/lib.

If you didn't put them there on purpose they could cause problems when
building Homebrew formulae, and may need to be deleted.

Unexpected static libraries:
    /usr/local/lib/libasprintf.a
    /usr/local/lib/libcharset.a
    /usr/local/lib/libexpat.a
    /usr/local/lib/libgettextpo.a
    /usr/local/lib/libintl.a

Unbrewed .la files were found in /usr/local/lib.

If you didn't put them there on purpose they could cause problems when
building Homebrew formulae, and may need to be deleted.

Unexpected .la files:
    /usr/local/lib/libasprintf.la
    /usr/local/lib/libcharset.la
    /usr/local/lib/libexpat.la
    /usr/local/lib/libgettextlib.la
    /usr/local/lib/libgettextpo.la
    /usr/local/lib/libgettextsrc.la
    /usr/local/lib/libiconv.la
    /usr/local/lib/libintl.la

Some directories in /usr/local/share/locale aren't writable.
This can happen if you "sudo make install" software that isn't managed
by Homebrew. If a brew tries to add locale information to one of these
directories, then the install will fail during the link step.
You should probably `chown` them:

    /usr/local/share/locale/be
    /usr/local/share/locale/be/LC_MESSAGES
    /usr/local/share/locale/bg
    /usr/local/share/locale/bg/LC_MESSAGES
    /usr/local/share/locale/ca
    /usr/local/share/locale/ca/LC_MESSAGES
    /usr/local/share/locale/cs
    /usr/local/share/locale/cs/LC_MESSAGES
    /usr/local/share/locale/da
    /usr/local/share/locale/da/LC_MESSAGES
    /usr/local/share/locale/de
    /usr/local/share/locale/de/LC_MESSAGES
    /usr/local/share/locale/el
    /usr/local/share/locale/el/LC_MESSAGES
    /usr/local/share/locale/en@boldquot
    /usr/local/share/locale/en@boldquot/LC_MESSAGES
    /usr/local/share/locale/en@quot
    /usr/local/share/locale/en@quot/LC_MESSAGES
    /usr/local/share/locale/eo
    /usr/local/share/locale/eo/LC_MESSAGES
    /usr/local/share/locale/es
    /usr/local/share/locale/es/LC_MESSAGES
    /usr/local/share/locale/et
    /usr/local/share/locale/et/LC_MESSAGES
    /usr/local/share/locale/eu
    /usr/local/share/locale/eu/LC_MESSAGES
    /usr/local/share/locale/fi
    /usr/local/share/locale/fi/LC_MESSAGES
    /usr/local/share/locale/fr
    /usr/local/share/locale/fr/LC_MESSAGES
    /usr/local/share/locale/ga
    /usr/local/share/locale/ga/LC_MESSAGES
    /usr/local/share/locale/gl
    /usr/local/share/locale/gl/LC_MESSAGES
    /usr/local/share/locale/hr
    /usr/local/share/locale/hr/LC_MESSAGES
    /usr/local/share/locale/hu
    /usr/local/share/locale/hu/LC_MESSAGES
    /usr/local/share/locale/id
    /usr/local/share/locale/id/LC_MESSAGES
    /usr/local/share/locale/it
    /usr/local/share/locale/it/LC_MESSAGES
    /usr/local/share/locale/ja
    /usr/local/share/locale/ja/LC_MESSAGES
    /usr/local/share/locale/ko
    /usr/local/share/locale/ko/LC_MESSAGES
    /usr/local/share/locale/nb
    /usr/local/share/locale/nb/LC_MESSAGES
    /usr/local/share/locale/nl
    /usr/local/share/locale/nl/LC_MESSAGES
    /usr/local/share/locale/nn
    /usr/local/share/locale/nn/LC_MESSAGES
    /usr/local/share/locale/pl
    /usr/local/share/locale/pl/LC_MESSAGES
    /usr/local/share/locale/pt
    /usr/local/share/locale/pt/LC_MESSAGES
    /usr/local/share/locale/pt_BR
    /usr/local/share/locale/pt_BR/LC_MESSAGES
    /usr/local/share/locale/ro
    /usr/local/share/locale/ro/LC_MESSAGES
    /usr/local/share/locale/ru
    /usr/local/share/locale/ru/LC_MESSAGES
    /usr/local/share/locale/sk
    /usr/local/share/locale/sk/LC_MESSAGES
    /usr/local/share/locale/sl
    /usr/local/share/locale/sl/LC_MESSAGES
    /usr/local/share/locale/sr
    /usr/local/share/locale/sr/LC_MESSAGES
    /usr/local/share/locale/sv
    /usr/local/share/locale/sv/LC_MESSAGES
    /usr/local/share/locale/tr
    /usr/local/share/locale/tr/LC_MESSAGES
    /usr/local/share/locale/uk
    /usr/local/share/locale/uk/LC_MESSAGES
    /usr/local/share/locale/vi
    /usr/local/share/locale/vi/LC_MESSAGES
    /usr/local/share/locale/wa
    /usr/local/share/locale/wa/LC_MESSAGES
    /usr/local/share/locale/zh_CN
    /usr/local/share/locale/zh_CN/LC_MESSAGES
    /usr/local/share/locale/zh_HK
    /usr/local/share/locale/zh_HK/LC_MESSAGES
    /usr/local/share/locale/zh_TW
    /usr/local/share/locale/zh_TW/LC_MESSAGES

==> /usr/bin occurs before /usr/local/bin
This means that system-provided programs will be used instead of those
provided by Homebrew. The following tools exist at both paths:

    easy_install
    easy_install-2.6
    emacs
    emacsclient
    etags
    iconv
    xmlwf

Consider editing your .bashrc to put /usr/local/bin
ahead of /usr/bin in your PATH.

gettext was detected in your PREFIX.

The gettext provided by Homebrew is "keg-only", meaning it does not
get linked into your PREFIX by default.

If you `brew link gettext` then a large number of brews that don't
otherwise have a `depends_on 'gettext'` will pick up gettext anyway
during the `./configure` step.

If you have a non-Homebrew provided gettext, other problems will happen
especially if it wasn't compiled with the proper architectures.

macportsの残骸が残っていた模様。(macports自体は既に存在していない）

やったこと(I'm trying that)

1. rm dylibs:
   rm /usr/local/lib/libasprintf.0.dylib /usr/local/lib/libcharset.1.0.0.dylib /usr/local/lib/libexpat.1.5.2.dylib /usr/local/lib/libgettextlib-0.18.dylib /usr/local/lib/libgettextpo.0.dylib /usr/local/lib/libgettextsrc-0.18.dylib /usr/local/lib/libiconv.2.2.0.dylib /usr/local/lib/libintl.8.dylib

2. rm static libraries:
   rm /usr/local/lib/libasprintf.a /usr/local/lib/libcharset.a /usr/local/lib/libexpat.a /usr/local/lib/libgettextpo.a /usr/local/lib/libintl.a

3. rm .la files:
   rm /usr/local/lib/libasprintf.la /usr/local/lib/libcharset.la /usr/local/lib/libexpat.la /usr/local/lib/libgettextlib.la /usr/local/lib/libgettextpo.la /usr/local/lib/libgettextsrc.la /usr/local/lib/libiconv.la /usr/local/lib/libintl.la

4. chown [me] /usr/local/share/locale

5. fixed non-existent symbolic link.

6. re-install gettext

$ brew install gettext
$ sudo brew link gettext
$ sudo brew unlink gettext

7. brew doctor

$ brew doctor
Your system is raring to brew.