Re: [PATCH] emacs: Avoid rebuilding .eldeps even when there's nothing to do

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+From: David Bremner <david@tethera.net>\r
+To: Austin Clements <amdragon@MIT.EDU>, notmuch@notmuchmail.org\r
+Subject: Re: [PATCH] emacs: Avoid rebuilding .eldeps even when there's\r
+       nothing to do\r
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+References: <m2iosade2y.fsf@guru.guru-group.fi>\r
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+Date: Fri, 21 Feb 2014 21:21:36 -0400\r
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+Austin Clements <amdragon@MIT.EDU> writes:\r
+\r
+> Previously, we updated .eldeps only if the file contents actually\r
+> needed to change.  This was done to avoid unnecessary make restarts\r
+> (if the .eldeps rule changes the mtime of .eldeps, make has to restart\r
+> to collect the new dependencies).  However, this meant that, after a\r
+> modification to any .el file that did not change dependencies, .eldeps\r
+> would always be out of date, so every make invocation would run the\r
+> .eldeps rule, which is both expensive because it starts up Emacs and\r
+> noisy.  This was true even when there was nothing to do.  E.g.,\r
+>\r
+\r
+pushed.\r
+\r
+d\r