Document HOMEBREW_DEBUG_INSTALL

Library/Contributions/manpages/brew.1.md

@@ -193,6 +193,11 @@ Some external commands are shipped with Homebrew, and enabled by default.
     If set, instructs Homebrew to always assume `--debug` when running
     commands.
 
+  * HOMEBREW\_DEBUG\_INSTALL:
+    When a `brew install -d` or `brew install -i` drops into a shell,
+    `HOMEBREW_DEBUG_INSTALL` will be set to the name of the formula being
+    tried.
+
   * HOMEBREW\_EDITOR:
     If set, Homebrew will use this editor when editing a single formula, or
     several formulae in the same folder.

share/man/man1/brew.1

@@ -203,6 +203,10 @@ HOMEBREW_DEBUG
 If set, instructs Homebrew to always assume \fB\-\-debug\fR when running commands\.
 .
 .TP
+HOMEBREW_DEBUG_INSTALL
+When a \fBbrew install \-d\fR or \fBbrew install \-i\fR drops into a shell, \fBHOMEBREW_DEBUG_INSTALL\fR will be set to the name of the formula being tried\.
+.
+.TP
 HOMEBREW_EDITOR
 If set, Homebrew will use this editor when editing a single formula, or several formulae in the same folder\.
 .