encoding: fix trim() to be O(n) instead of O(n^2)
`encoding.trim()` iterated over the possible lengths smaller than the
input and created a slice for each. It then calculated the column
width of the result, which is of course O(n), so the overall algorithm
was O(n). This patch rewrites it to iterate over the unicode
characters, keeping track of the length so far. Also, the old
algorithm started from the end of the string, which made it much worse
when the input is large and the limit is small (such as the typical 72
we pass to it).
You can time it by running something like this:
```
time python3 -c 'from mercurial.utils import stringutil; print(stringutil.ellipsis(b"0123456789" * 1000, 5))'
```
That drops from 4.05 s to 83 ms with this patch (and most of that is
of course startup time).
Differential Revision: https://phab.mercurial-scm.org/D12089
#require serve
$ cat > web.conf << EOF
> [paths]
> / = $TESTTMP/*
> EOF
$ hg init repo1
$ cd repo1
$ touch foo
$ hg -q commit -A -m initial
$ cd ..
$ hg serve -p $HGPORT -d --pid-file=hg.pid --web-conf web.conf
$ cat hg.pid >> $DAEMON_PIDS
repo index should not send Content-Security-Policy header by default
$ get-with-headers.py --headeronly localhost:$HGPORT '' content-security-policy etag
200 Script output follows
static page should not send CSP by default
$ get-with-headers.py --headeronly localhost:$HGPORT static/mercurial.js content-security-policy etag
200 Script output follows
repo page should not send CSP by default, should send ETag
$ get-with-headers.py --headeronly localhost:$HGPORT repo1 content-security-policy etag
200 Script output follows
etag: W/"*" (glob)
$ killdaemons.py
Configure CSP without nonce
$ cat >> web.conf << EOF
> [web]
> csp = script-src https://example.com/ 'unsafe-inline'
> EOF
$ hg serve -p $HGPORT -d --pid-file=hg.pid --web-conf web.conf
$ cat hg.pid > $DAEMON_PIDS
repo index should send Content-Security-Policy header when enabled
$ get-with-headers.py --headeronly localhost:$HGPORT '' content-security-policy etag
200 Script output follows
content-security-policy: script-src https://example.com/ 'unsafe-inline'
static page should send CSP when enabled
$ get-with-headers.py --headeronly localhost:$HGPORT static/mercurial.js content-security-policy etag
200 Script output follows
content-security-policy: script-src https://example.com/ 'unsafe-inline'
$ get-with-headers.py --twice --headeronly localhost:$HGPORT repo1/static/style.css content-security-policy
200 Script output follows
content-security-policy: script-src https://example.com/ 'unsafe-inline'
304 Not Modified
content-security-policy: script-src https://example.com/ 'unsafe-inline'
repo page should send CSP by default, include etag w/o nonce
$ get-with-headers.py --headeronly localhost:$HGPORT repo1 content-security-policy etag
200 Script output follows
content-security-policy: script-src https://example.com/ 'unsafe-inline'
etag: W/"*" (glob)
nonce should not be added to html if CSP doesn't use it
$ get-with-headers.py localhost:$HGPORT repo1/graph/tip | egrep 'content-security-policy|<script'
<script type="text/javascript" src="/repo1/static/mercurial.js"></script>
<script type="text/javascript">
<script type="text/javascript">
Configure CSP with nonce
$ killdaemons.py
$ cat >> web.conf << EOF
> csp = image-src 'self'; script-src https://example.com/ 'nonce-%nonce%'
> EOF
$ hg serve -p $HGPORT -d --pid-file=hg.pid --web-conf web.conf
$ cat hg.pid > $DAEMON_PIDS
nonce should be substituted in CSP header
$ get-with-headers.py --headeronly localhost:$HGPORT '' content-security-policy etag
200 Script output follows
content-security-policy: image-src 'self'; script-src https://example.com/ 'nonce-*' (glob)
nonce should be included in CSP for static pages
$ get-with-headers.py --headeronly localhost:$HGPORT static/mercurial.js content-security-policy etag
200 Script output follows
content-security-policy: image-src 'self'; script-src https://example.com/ 'nonce-*' (glob)
repo page should have nonce, no ETag
$ get-with-headers.py --headeronly localhost:$HGPORT repo1 content-security-policy etag
200 Script output follows
content-security-policy: image-src 'self'; script-src https://example.com/ 'nonce-*' (glob)
nonce should be added to html when used
$ get-with-headers.py localhost:$HGPORT repo1/graph/tip content-security-policy | egrep 'content-security-policy|<script'
content-security-policy: image-src 'self'; script-src https://example.com/ 'nonce-*' (glob)
<script type="text/javascript" src="/repo1/static/mercurial.js"></script>
<script type="text/javascript" nonce="*"> (glob)
<script type="text/javascript" nonce="*"> (glob)
hgweb_mod w/o hgwebdir works as expected
$ killdaemons.py
$ hg serve -R repo1 -p $HGPORT -d --pid-file=hg.pid --config "web.csp=image-src 'self'; script-src https://example.com/ 'nonce-%nonce%'"
$ cat hg.pid > $DAEMON_PIDS
static page sends CSP
$ get-with-headers.py --headeronly localhost:$HGPORT static/mercurial.js content-security-policy etag
200 Script output follows
content-security-policy: image-src 'self'; script-src https://example.com/ 'nonce-*' (glob)
nonce included in <script> and headers
$ get-with-headers.py localhost:$HGPORT graph/tip content-security-policy | egrep 'content-security-policy|<script'
content-security-policy: image-src 'self'; script-src https://example.com/ 'nonce-*' (glob)
<script type="text/javascript" src="/static/mercurial.js"></script>
<script type="text/javascript" nonce="*"> (glob)
<script type="text/javascript" nonce="*"> (glob)