One of the proposals in #23328

This PR introduces a simple expression calculator
(templates/eval/eval.go), it can do basic expression calculations.

Many untested template helper functions like `Mul` `Add` can be replaced
by this new approach.

Then these `Add` / `Mul` / `percentage` / `Subtract` / `DiffStatsWidth`
could all use this `Eval`.

And it provides enhancements for Golang templates, and improves
readability.

Some examples:

----

* Before: `{{Add (Mul $glyph.Row 12) 12}}`
* After: `{{Eval $glyph.Row "*" 12 "+" 12}}`

----

* Before: `{{if lt (Add $i 1) (len $.Topics)}}`
* After: `{{if Eval $i "+" 1 "<" (len $.Topics)}}`

## FAQ

### Why not use an existing expression package?

We need a highly customized expression engine:

* do the calculation on the fly, without pre-compiling
* deal with int/int64/float64 types, to make the result could be used in
Golang template.
* make the syntax could be used in the Golang template directly
* do not introduce too much complex or strange syntax, we just need a
simple calculator.
* it needs to strictly follow Golang template's behavior, for example,
Golang template treats all non-zero values as truth, but many 3rd
packages don't do so.

### What's the benefit?

* Developers don't need to add more `Add`/`Mul`/`Sub`-like functions,
they were getting more and more.
Now, only one `Eval` is enough for all cases.
* The new code reads better than old `{{Add (Mul $glyph.Row 12) 12}}`,
the old one isn't familiar to most procedural programming developers
(eg, the Golang expression syntax).
* The `Eval` is fully covered by tests, many old `Add`/`Mul`-like
functions were never tested.

### The performance?

It doesn't use `reflect`, it doesn't need to parse or compile when used
in Golang template, the performance is as fast as native Go template.

### Is it too complex? Could it be unstable?

The expression calculator program is a common homework for computer
science students, and it's widely used as a teaching and practicing
purpose for developers. The algorithm is pretty well-known.

The behavior can be clearly defined, it is stable.

Follow #21429 & #22861

Use `<gitea-locale-number>` instead of backend `PrettyNumber`. All old
`PrettyNumber` related functions are removed. A lot of code could be
simplified.

And some functions haven't been used for long time (dead code), so they
are also removed by the way (eg: `SplitStringAtRuneN`, `Dedent`)

This PR only tries to improve the `PrettyNumber` rendering problem, it
doesn't touch the "plural" problem.

Screenshot:


![image](https://user-images.githubusercontent.com/2114189/229290804-1f63db65-1e34-4a54-84ba-e00b44331b17.png)


![image](https://user-images.githubusercontent.com/2114189/229290911-c88dea00-b11d-48dd-accb-9f52edd73ce4.png)

Change all license headers to comply with REUSE specification.

Fix #16132

Co-authored-by: flynnnnnnnnnn <flynnnnnnnnnn@github>
Co-authored-by: John Olheiser <john.olheiser@gmail.com>

This PR adds a generic set type to get rid of maps used as sets.

Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>

* Prettify number of issues

- Use the PrettyNumber function to add commas in large amount of issues.

* Use client-side formatting

* prettify on both server and client

* remove unused i18n entries

* handle more cases, support other int types in PrettyNumber

* specify locale to avoid issues with node default locale

* remove superfluos argument

* introduce template helper, octicon tweaks, js refactor

* Update modules/templates/helper.go

* Apply some suggestions.

* Add comment

* Update templates/user/dashboard/issues.tmpl

Co-authored-by: silverwind <me@silverwind.io>

Co-authored-by: silverwind <me@silverwind.io>
Co-authored-by: Lunny Xiao <xiaolunwen@gmail.com>

* Added type sniffer.

* Switched content detection from base to typesniffer.

* Added GuessContentType to Blob.

* Moved image info logic to client.
Added support for SVG images in diff.

* Restore old blocked svg behaviour.

* Added missing image formats.

* Execute image diff only when container is visible.

* add margin to spinner

* improve BIN tag on image diffs

* Default to render view.

* Show image diff on incomplete diff.

Co-authored-by: silverwind <me@silverwind.io>
Co-authored-by: Lunny Xiao <xiaolunwen@gmail.com>
Co-authored-by: Lauris BH <lauris@nix.lv>

* fix truncate utf8 string.

* revoke truncated user info.

* fix url

* modules/auth/pa: coverage: 40#.0%

* modules/base coverage: 67.6% -> 89.9%

* modules/cache coverage: 0% -> 12.0%

* modules/convert coverage: 27.1% -> 29.7%

* make svg regex case-insensitive & use strict word boundary

* allow doctype svg

* add doctype tests

* allow <!DOCTYPE svg> and <svg/>

* Change to display SVG files as images

* Remove unsafe styles from SVG CSP

* Add integration test to test SVG headers

* Add config setting to disable SVG rendering

* Add test for img tag when loading SVG image

* Remove the Raw view button for svg files since we don't fully support this

* Fix copyright year

* Rename and move config setting

* Add setting to cheat sheet in docs

* Fix so that comment matches cheat sheet

* Add allowing styles in CSP based on pull request feedback

* Re-enable raw button since we show SVG styles now

* Change so that SVG files are editable

* Add UI to toggle between source and rendered image for SVGs

* Change to show blame button for SVG images

* Fix to update ctx data

* Add test for DetectContentType when file is longer than sniffLen

Co-authored-by: Jonathan Tran <jon@allspice.io>
Co-authored-by: Kyle D <kdumontnu@gmail.com>

* Fix panic in BasicAuthDecode

If the string does not contain ":" that function would run into an
`index out of range [1] with length 1` error. prevent that.

* Update BasicAuthDecode()

Co-authored-by: 6543 <6543@obermui.de>

* Direct avatar rendering

This adds new template helpers for avatar rendering which output image
elements with direct links to avatars which makes them cacheable by the
browsers.

This should be a major performance improvment for pages with many avatars.

* fix avatars of other user's profile pages

* fix top border on user avatar name

* uncircle avatars

* remove old incomplete avatar selector

* use title attribute for name and add it back on blame

* minor refactor

* tweak comments

* fix url path join and adjust test to new result

* dedupe functions

* Use a simple format for the big number on ui

Signed-off-by: a101211279 <1012112796@qq.com>

* make fmt

* Apply review suggestion @silverwind

* Change name 2

* make fmt

Co-authored-by: Lunny Xiao <xiaolunwen@gmail.com>

* Add copyright

Signed-off-by: jolheiser <john.olheiser@gmail.com>

* Add gitea-vet and fix non-compliance

Signed-off-by: jolheiser <john.olheiser@gmail.com>

* Combine tools.go into build.go and clean up

Signed-off-by: jolheiser <john.olheiser@gmail.com>

* Remove extra GO111MODULE=on

Signed-off-by: jolheiser <john.olheiser@gmail.com>

speed up page generation by making avatar lookup occur at the browser
not at page generation

* Protect against evil email address ".."

* hash the complete email address

Signed-off-by: Andrew Thornton <art27@cantab.net>

Co-Authored-By: Lauris BH <lauris@nix.lv>

* Show download count info in release list

* Use go-humanize

* display ui time with customize time location

* fix lint

* rename UILocation to DefaultUILocation

* move time related functions to modules/timeutil

* fix tests

* fix tests

* fix build

* fix swagger

* Convert files to utf-8 for indexing

* Move utf8 functions to modules/base

* Bump repoIndexerLatestVersion to 3

* Add tests for base/encoding.go

* Changes to pass gosimple

* Move UTF8 funcs into new modules/charset package

* refactor: append, build variable and type switch

* fix: remove redundant space.

Signed-off-by: Codruț Constantin Gușoi <codrut.gusoi@gmail.com>

* Fix avatar URLs

* import order

* Use identicon image for default gravatar.

* Fixed tests.

* xxx_active_code_live setting in printed in hours and minutes instead of just hours

* Update app.ini description of xxx_code_lives settings

* Moved conf assets into options folder

* Dropped old bindata

* Started to integrate options bindata and accessors

* Do not enforce a builtin app.ini

* Replaced bindata calls with options

* Dropped bindata task from makefile, it's the generate task now

* Always embedd app.ini to provide sane config defaults

* Use sane defaults for the configuration

* Defined default value for SSH_KEYGEN_PATH

* Dropped "NEVER EVER MODIFY THIS FILE" header from app.ini

* Fixed new paths in latest test additions

* Drop bindata with make clean task

* Set more proper default values

Also address other TODOs

* Remove unused custom-alphabet feature of random string generator

Fix random string generator

Random string generator should return error if it fails to read random data via crypto/rand

* Fixes variable (un)initialization mixed assign
Update test GetRandomString

- Update import paths from github.com/go-gitea to code.gitea.io
- Fix import path for travis

See https://docs.travis-ci.com/user/languages/go#Go-Import-Path