Makefile: fold MISC_H into LIB_H

We keep a list of most of the header files in LIB_H, but some are split out into MISC_H. The original point of LIB_H was that it would force recompilation of C files when any of the library headers changed. It was over-encompassing, since not all C files included all of the library headers; this made it simple to maintain, but meant that we sometimes recompiled when it was not necessary. Over time, some new headers were omitted from LIB_H, and rules were added to the Makefile for a few specific targets to explicitly depend on them. This avoided some unnecessary recompilation at the cost of having to maintain the dependency list of those targets manually (e.g., d349a03). Later, we needed a complete list of headers from which we should extract strings to localized. Thus 1b8b2e4 introduced MISC_H to mention all header files not included in LIB_H, and the concatenation of the two lists is fed to xgettext. Headers mentioned as dependencies must also be manually added to MISC_H to receive the benefits of localization. Having to update multiple locations manually is a pain and has led to errors. For example, see "git log -Swt-status.h Makefile" for some back-and-forth between the two locations. Or the fact that column.h was never added to MISC_H, and therefore was not localized (which is fixed by this patch). Moreover, the benefits of keeping these few headers out of LIB_H is not that great, for two reasons: 1. The better way to do this is by auto-computing the dependencies, which is more accurate and less work to maintain. If your compiler supports it, we turn on computed header dependencies by default these days. So these manual dependencies are used only for people who do not have gcc at all (which increases the chance of them becoming stale, as many developers will never even use them). 2. Even if you do not have gcc, the manual header dependencies do not help all that much. They obviously cannot help with an initial compilation (since their purpose is to avoid unnecessary recompilation when a header changes), which means they are only useful when building a new version of git in the working tree that held an existing build (e.g., after checkout or during a bisection). But since a change of a header in LIB_H will force recompilation, and given that the vast majority of headers are in LIB_H, most version changes will result in a full rebuild anyway. Let's just fold MISC_H into LIB_H and get rid of these manual rules. The worst case is some extra compilation, but even that is unlikely to matter due to the reasons above. The one exception is that we should keep common-cmds.h separate. Because it is generated, the computed dependencies do not handle it properly, and we must keep separate individual dependencies on it. Let's therefore rename MISC_H to GENERATED_H to make it more clear what should go in it. Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>