I observed that `eglot' would happily start dozens of language server
processes, but each one of them only seemed to know about a tiny
fraction of my code. I tracked this down and found a minor bug in
project.el.

In `project-try-vc', when `vc-handled-backends' is nil, the value of
`marker-re' computed here:

https://git.savannah.gnu.org/cgit/emacs.git/tree/lisp/progmodes/project.el?id=207901457c018d94b1ce9e13a897d8241b1f3af2#n516

is the empty string.

If no vc backends are enabled, no directory should be treated as a vc
root. But the empty regexp matches everything, so *all* directories are
treated as vc roots.

Consequently, `eglot' spawned a lot of processes, because it starts one
per project.

The workaround is to set `vc-handled-backends' to any other value. (I
suppose I configured it to nil long ago, when working in a huge
Mercurial repository. Back then, commonplace hg commands in that repo
were unreasonably slow.)

In GNU Emacs 27.2 (build 1, x86_64-apple-darwin18.7.0, NS appkit-1671.60 Version 10.14.6 (Build 18G95))
 of 2021-03-27 built on builder10-14.porkrind.org
Windowing system distributor 'Apple', version 10.3.2299
System Description:  macOS 13.0.1

Recent messages:
(".git")
project-try-vc-2
"~/src/blackbird/"
Quit
Followed link to /Users/jorendorff/src/dotfiles/.emacs
Mark set [3 times]
Quit
Making completion list...
Type "q" to restore previous buffer.
user-error: No cross-reference here
Quit
Configured using:
 'configure --with-ns '--enable-locallisppath=/Library/Application
 Support/Emacs/${version}/site-lisp:/Library/Application
 Support/Emacs/site-lisp' --with-modules'

Configured features:
NOTIFY KQUEUE ACL GNUTLS LIBXML2 ZLIB TOOLKIT_SCROLL_BARS NS MODULES
THREADS JSON PDUMPER GMP

Important settings:
  value of $LANG: en_US.UTF-8
  locale-coding-system: utf-8-unix

Major mode: Info

Minor modes in effect:
  show-paren-mode: t
  global-git-commit-mode: t
  magit-auto-revert-mode: t
  shell-dirtrack-mode: t
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  tooltip-mode: t
  global-eldoc-mode: t
  electric-indent-mode: t
  mouse-wheel-mode: t
  file-name-shadow-mode: t
  global-font-lock-mode: t
  font-lock-mode: t
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  column-number-mode: t
  line-number-mode: t
  transient-mark-mode: t

Load-path shadows:
/Users/jorendorff/.emacs.d/elpa/jsonrpc-1.0.15/jsonrpc hides /Applications/Emacs.app/Contents/Resources/lisp/jsonrpc
/Users/jorendorff/.emacs.d/elpa/xref-1.6.0/xref hides /Applications/Emacs.app/Contents/Resources/lisp/progmodes/xref
/Users/jorendorff/.emacs.d/elpa/project-0.9.3/project hides /Applications/Emacs.app/Contents/Resources/lisp/progmodes/project
/Users/jorendorff/.emacs.d/elpa/flymake-1.2.2/flymake hides /Applications/Emacs.app/Contents/Resources/lisp/progmodes/flymake
/Users/jorendorff/.emacs.d/elpa/seq-2.23/seq hides /Applications/Emacs.app/Contents/Resources/lisp/emacs-lisp/seq
/Users/jorendorff/.emacs.d/elpa/eldoc-1.13.0/eldoc hides /Applications/Emacs.app/Contents/Resources/lisp/emacs-lisp/eldoc

Features:
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edmacro kmacro magit-git magit-base magit-section format-spec crm
compat-27 compat-26 compat compat-macs eglot array filenotify jsonrpc
ert pp ewoc debug backtrace xref flymake-proc flymake thingatpt warnings
compile comint ring pcase url-util project imenu flycheck ansi-color
find-func rx dash cl-extra help-mode use-package use-package-ensure
use-package-delight use-package-diminish use-package-bind-key bind-key
easy-mmode use-package-core finder-inf info package easymenu browse-url
url-handlers url-parse auth-source cl-seq eieio eieio-core cl-macs
eieio-loaddefs password-cache json subr-x map url-vars seq byte-opt gv
bytecomp byte-compile cconv cl-loaddefs cl-lib tooltip eldoc electric
uniquify ediff-hook vc-hooks lisp-float-type mwheel term/ns-win ns-win
ucs-normalize mule-util term/common-win tool-bar dnd fontset image
regexp-opt fringe tabulated-list replace newcomment text-mode elisp-mode
lisp-mode prog-mode register page tab-bar menu-bar rfn-eshadow isearch
timer select scroll-bar mouse jit-lock font-lock syntax facemenu
font-core term/tty-colors frame minibuffer cl-generic cham georgian
utf-8-lang misc-lang vietnamese tibetan thai tai-viet lao korean
japanese eucjp-ms cp51932 hebrew greek romanian slovak czech european
ethiopic indian cyrillic chinese composite charscript charprop
case-table epa-hook jka-cmpr-hook help simple abbrev obarray
cl-preloaded nadvice loaddefs button faces cus-face macroexp files
text-properties overlay sha1 md5 base64 format env code-pages mule
custom widget hashtable-print-readable backquote threads kqueue cocoa ns
multi-tty make-network-process emacs)

Memory information:
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 (vectors 16 106459)
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