Fixes a crash regression introduced when fetch/send were made to close the work tree earlier.

If the child has exited for some reason then we won't be able to send a stop message on the pipe. Ignore such errors while we are tearing a repository data structure down. The error should be harmless but can trip up gotwebd when cycling repositories out of its repo cache: gotwebd[29683]: gotweb_render_index: got-portable.git: unexpected end of file

and use it to avoid hardcoding the digest type in a few places. ok stsp@

it abstracts over the hash type and ensures that object ids are zero'ed before their sha1 digest is written. Needed by the incoming sha256 support. ok stsp@

It will soon grow functions to deal with sha256 too. stsp@ agrees.

In preparation for wide sha256 support; stsp@ agrees. Change done mechanically with find . -iname \*.[cy] -exec sam {} + X ,x/<sha1\.h>/i/\n#include <sha2.h>

reported by Lucas on IRC, who sent a patch which this commit was based on ok jamsek

Most extension allow only for a boolean value so the current behaviour of just sending the extension with a trueish value is fine. However, some extensions that we could eventually support (like "objectformat") have a string value. This is a preparatory step towards that. ok stsp@

got_repo_get_gitconfig_extensions is only used in gotadmin to check if the preciousObjects extension is active; let's replace it with a function that just checks whether a certain extension is active. It simplifies future changes to the extensions handling. ok stsp@

Accept flag parameter to optionally specify which pointers to free. This saves callers looping through the list to free pointers. ok + fix stsp@

ok op@

Convert from st.m_time (second-precision time_t) to st.m_tim (struct timespec). To compensate for the potential case where a filesystem provides resolution in seconds only, always read the directory if no pack files are known to exist. Otherwise, there is a race condition when gotd repo_write creates a new pack and a request arrives for repo_read shortly after. Caught by a regression test for gotd on empty repositories. Test failure pointed out by Mikhail. ok op@

ok op@

It's only a preparatory step, as checking whether a size_t is less than SIZE_MAX is moot. In a follow-up commit, however, the `filesize' field of the struct got_pack will become off_t and these checks will kick in. This also makes consistent how we guard mmap(2) against empty files. ok and improvements stsp@